Construction and maintenance of national highways is looked after by Central government. National Highways Authority of India was constituted by an Act. of Parliament, namely the National Highways Authority of India Act , 1988, to develop, maintain and manage the National Highways vested or entrusted to it by the Central Government. The Authority is mandated to develop, maintain and manage the national highways and any other highways vested in, or entrusted to, it by the Government.

Vehicles are a major pollution contributor. Vehicles produce significant amounts of nitrogen oxides, carbon monoxide, and other pollution. Cycle is the vehicle which does not pollute the environment. Cycles do not need fossil fuels, so that they do not emit any harmful gases. So, cycle is an eco-friendly mode of transport. Cycling 10 km each way to work would save 1500 kg of greenhouse gas emissions each year. Cycling has health benefits too.

National Highways are main highways running through the length and breadth of the country connecting major ports, state capitals, large industrial and tourist centers, etc. National Highways in India are designated as NH followed by the highway number. The traffic on National Highways has been growing due to the recent economic growth in India and the Government of India is taking steps to improve management techniques to provide hindrance-free traffic movement by way of widening roads, grade separation, construction of bypasses, bridges, rail-road crossings, and utilizing the latest technologies. Even though the National Highways represent only 2% of the total network length, they handle about 40% of the total road traffic.

NH-44 is the longest highway in India. Previously this highway was known as NH-07. It starts from Varanasi (Uttar Pradesh) and ends at Kanyakumari (Tamilnadu). This highway acts a major link between the north and south of India. It runs through the states of Uttar Pradesh, Madhya Pradesh, Maharashtra, Telangana, Andhra Pradesh, Karnataka, and Tamil Nadu. Its total length is over 2,369 km.

The Grand Trunk Road is commonly known as the G.T. Road. It is the oldest, longest, and most famous highway in the Indian subcontinent.

D.  Kerela

Nedimbacherry International Airport also now known as the Cochin International Airport is located in Nedumbassery. Nedumbassery is a suburb of the city of Kochi situated 27 kilometers (17 mi) north of the city and 53 km from Thrissur in Kerala, India. 

C. Indira Gandhi

Indira Gandhi International Airport serves as the primary civilian aviation hub for the National Capital Region of Delhi, India. The airport, spread over an area of 5,106 acres (2,066 ha),is situated in Palam, 15 km (9.3 mi) south-west of the New Delhi railway station and 16 km (9.9 mi) from New Delhi city center. Named after Indira Gandhi, a former Prime Minister of India, it is the busiest airport in the country in terms of passenger traffic since 2009.

B. Rajiv Gandhi International Airport

Roads linking a state capital with different district headquarters are known as State Highways. These roads are constructed and maintained by the State Public Works Department (PWD) in State and Union Territories. 

North-South corridor would connect Srinagar in Jammu and Kashmir with Kanyakumari in Tamil Nadu with a 4,076 km long road. The major objective of these Super Highways is to reduce the time and distance between the mega cities of India. These highway projects are being implemented by the National Highway Authority of India (NHAI).

Kerala has the highest road density in India followed by Tripura. Kerala has a road network of 5,268.69 km per 1,000 sq km.

National Highway 7 or NH 7, is major North-South National Highway in India that runs through the states of Uttar Pradesh, Madhya Pradesh, Maharashtra, Andhra Pradesh, Karnataka, and Tamil Nadu. NH-7 was laid and is maintained by Central Public Works Department (CPWD). This highway starts from the area Hyderabad Gate in Varanasi and ends Near Kanyakumari Railway Station with junction of Tamil Nadu State highway no. 179.

The major objective of these Super Highways is to reduce the time and distance between the mega cities of India. These highway projects are being implemented by the National Highway Authority of India (NHAI). 

National Highway 7 is renamed as National Highway 44, The 2,369 km long road is the longest National Highway of India and one of the major road network between south and north India. The National Highway 44 cross 6 Indian states and connects major Indian cities like Varanasi,Nagpur, Hyderabad,Bangalore and Madurai. Some of the part of NH7 or NH44 is selected as North-South Corridor and Golden Quadrilateral highway projects.

North-South Corridor would connect Srinagar in Jammu and Kashmir with Kanyakumari in Tamil Nadu with a 4,076 km long road.

Non-Renewable Resources: Minerals and fossil fuels are examples of such resources. These resources take millions of years in their formation.  Some of the resources like metals are recyclable and some like fossil fuels cannot be recycled and get exhausted with their use.

Industries, apart from being heavy users of water, also require power to run them. Much of this energy comes from hydroelectric power. Today, in India hydroeclectric power contributes approximately 22 per cent of the total electricity produced.

The NHAI was constituted in 1988. It is responsible for the development, maintenance and management of National Highways. It was made operational in February 1995 and is currently undertaking the developmental activities under National Highways Development Project (NHDP) in phases.

The Golden Quadrilateral is the largest express highway project in India. It connects India's four largest metropolises: Chennai, Kolkata, Mumbai and Delhi, and thus forms a quadrilateral of sorts.

In terms of power generation, India is the sixth largest state. About 65% of electricity consumed in India is generated by thermal power plants, 22% by hydroelectric power plants, 3% by nuclear power plants and rest 10% by alternative sources of energy such as solar, biomass etc. Thus, chief source is thermal power plants.

The Golden Quadrilateral (GQ) is a national highway network connecting most of the major industrial, agricultural and cultural centers of India. It forms a quadrilateral connecting the four major metro cities of India, viz., Delhi (north), Kolkata (East), Mumbai (west) and Chennai (south).

At 5,846 kilometers (3,633 mi), it is the largest highway project in India and the fifth-longest in the world. It is the first phase of the National Highways Development Project (NHDP), and consists of four- and six-lane express highways

India was one of the pioneering countries in establishing hydro-electric power plants. The power plants at Darjeeling and Shimsha were established in 1898 and 1902 respectively and is one of the first in Asia.

It was launched in December 2000 by the Government of India to provide connectivity to rural areas as part of a poverty eradication measure. 

Korba is the Indian state of chhattisgarh. It is famous for its Korba Super Thermal Power Plant which is located at Jamnipali. It is one of the coal based power plants of National Thermal Power Corporation (NTPC). The coal for the power plants is sourced from Kusmunda and Gevra mines.

• The Grand Trunk Road is not only in India's but one of the of South Asia's oldest and longest major roads. The road often called the "Gernaili Sadak" (the Generals' Road) and Sadak-e-Azam ('The Grand Road') covers a distance of over 2,500 kilometers (1,600 mi). It was built by Sher Shah Suri.
  
• At present, it extends from Amritsar to Kolkata. It is bifurcated into 2 segments : (a) National Highway (NH)-1 from Delhi to Amritsar, and (b) NH- 2 from Delhi to Kolkata.
  

Koyna power plant is situated in Satara district near Patan and taken over by government of Maharasthra after independence. It is a complex project with four dams with largest dam on Koyna River and hence the name Koyna hydel power plant. 

Sher Shah Suri built the Shahi (Royal) road to strengthen and consolidate his empire from the Indus Valley to the Sonar Valley in Bengal. This road was renamed the Grand Trunk (GT) road during the British period, connecting Calcutta and Peshawar. At present, it extends from Amritsar to Kolkata. It is bifurcated into 2 segments : (a) National Highway(NH)-1 from Delhi to Amritsar, and (b) NH- 2 from Delhi to Kolkata.

• Road density is the ratio of the length of the country's total road network to the country's land area. It is expressed in km of state roads per 100 km².
  
• The distribution of roads is highly uneven in India. The road density is highest in Kerala with 375 kms and the least in Jammu & Kashmir with just 10 kms.
  

The National Highway 7 is the longest national highway. It starts at Varanasi in North India and ends at Kanyakumari in South India.

This organization was established in 1960 for the development of the roads of strategic importance in the northern and northeastern border areas. These roads have improved accessibility in areas of difficult terrain and have helped in the economic development of these areas. It was formed on May 7^th, 1960.

Zojila Pass-9 kilometers from Sonamarg and at an elevation of 3500 meters above sea level, is responsible for connecting Kashmir Valley to Ladakh Valley

Manali-Leh highway is notorious for its avalanches and landslides. During winter months the terrain becomes difficult and is mostly covered with snow most of the time

• Pradhan Mantri Sadak Yojna is a nationwide scheme to connect all unconnected rural villages by roads. This was introduced in the year 2000.
  
• It is under the authority of Ministry of Roads.
  

Maharashtra has highest national highway network.

The main national highways in Maharashtra are: NH 3, NH 50, NH 69, NH 7, NH 17, NH 211, NH 204, NH 4, NH 8, NH 9, NH 13, NH 16, NH 4B, NH 6, and NH 222. Total length of highways in the state of Maharashtra exceeds 3700 kms. Almost 98% villages are connected via the highways and modern roads in Maharashtra.

• Flyover- An overpass which crosses another road or railway line.
  
• Expressway- A high-speed road with partial access and extra facilities.
  
• Subway- A tunnel under a road for use by pedestrians.
  
• Highways- A generic term given to roadways used to connect important cities.
  

India has a vast road network. It has the second largest road network in the world. It has the roads connecting almost all parts of the country including rural areas and remote parts. In India the border roads passes through 12 states of the country.

India has one of the largest road networks in the world, aggregating to about 2.3 million km at present. In India, roadways have preceded railways. 

 The historical Sher-Shah Suri Marg is called National Highway No.1, between Delhi and Amritsar.

 National Highways link extreme parts of the country. These are the primary road systems and are laid and maintained by the Central Public Works Department (CPWD). 

Golden Quadrilateral is a network of four or six-lane highways which connects top four metropolitan cities of India, namely Delhi, Mumbai, Chennai, and Kolkata, thereby, forming a quadrilateral. It is the largest highway project in India. The Golden Quadrilateral project was launched in 2001 as part of National Highways Development Project. Its overall length is 5,846km.

Subways are the roads which are constructed under the ground. A subway is normally an underpass for pedestrians or cyclists beneath a road or railway. It allows them to reach the other side in safety. Subways are found in countries like England and Wales, the Republic of Ireland, Hong Kong and Commonwealth countries such as India, South Africa, Australia and New Zealand.

National Highways link extreme parts of the country. These are the primary road systems and are laid and maintained by the Central Public Works Department (CPWD). A number of major National Highways run in North-South and East-West directions. The historical Sher-Shah Suri Marg is called National Highway No.1, between Delhi and Amritsar. Currently the longest highway in India is NH-44, starting from Kanyakumari in Tamil Nadu to Srinagar of Jammu and Kashmir. As per old numbering, a part of this highway was called NH 7, whose northern end was Varanasi of Uttar Pradesh.

The correct answer is 21.

Currently, the BRO (Boarder Road Organization) maintains operations in twenty-one states, one UT (Andaman and Nicobar Islands), and neighboring countries such as Afghanistan, Bhutan, Myanmar, and Sri Lanka. The BRO operates and maintains over 32,885 kilometers of roads and about 12,200 meters of permanent bridges in the country. Presently, BRO is also involved in the construction of a tunnel at the Rohtang pass which is estimated to be ready by 2019. It is currently headed by Lt General Suresh Sharma who is the 24th Director General Border Roads (DGBR)

Pandit Jawaharlal Nehru, the great visionary and first Prime Minister of India conceptualized Border Roads Organization in 1960. The organization primarily meets the defence requirement towards infrastructure development of remote Border areas of North & North East states.

The Border Roads Organisation (BRO) develops and maintains road networks in India's border areas and friendly neighboring countries. Officers from the Border Roads Engineering Service (BRES) and personnel from the General Reserve Engineer Force (GREF) form the parent cadre of the Border Roads Organisation

Kerala has the highest road density and Jammu & Kashmir (J&K) has the lowest road density.

In terms of power generation, India is the sixth largest state. About 65% of electricity consumed in India is generated by thermal power plants, 22% by hydroelectric power plants, 3% by nuclear power plants and rest 10% by alternative sources of energy such as solar, biomass etc.

Old National Highway 2 or Old NH 2, (currently National Highway 19 (India)) was a major National Highway in India, that connected the states of Delhi, Haryana, Uttar Pradesh, Bihar, Jharkhand, and West Bengal. It constitutes a major portion of the historical Grand Trunk Road along with old NH 91 and old NH 1 in India.

The National Highways Authority of India (NHAI) is the nodal agency responsible for building, upgrading, and maintaining most of the National Highways network. It operates under the Ministry of Road Transport and Highways of the Central Government.

The National Highways Authority of India was established by the National Highways Authority of India Act, 1988. Section 16(1) of the Act states that the function of NHAI is to develop, maintain, and manage the National Highways and any other highways vested in, or entrusted to, it by the Government of India.

The Golden Quadrilateral is a national highway network connecting most of the major industrial, agricultural and cultural centers of India. It forms a quadrilateral connecting the four major metro cities of India, viz., Delhi, Kolkata, Mumbai, and Chennai.

The Hindustan-Tibet road connecting Shimla with Gangtok in Western Tibet passes through the Shipki la.

• Road density is the ratio of the length of the country's total road network to the country's land area. It is expressed in km of state roads per 100 km².
  
• Japan has road density 12 times greater than India. 
  

• The longest National highway in India is NH-7 which is now called NH 44. It starts from Srinagar in the north and terminates in Kanyakumari in south. It passes through the states of Jammu & Kashmir, Punjab, Haryana, Delhi, Uttar Pradesh, Madhya Pradesh, Maharashtra, Telangana, Andhra Pradesh, Karnataka, and Tamil Nadu. It includes cities of Nagpur - Jabalpur- Bangalore - Hyderabad – Madurai. 

1. National Highway 8 (NH 8) is a 4-lane (6-lane in most parts of Gujarat and between Delhi-Jaipur) National Highway in India.
2. It connects the national capital Delhi to the financial capital Mumbai, as well as important cities Gurgaon, Jaipur, Ajmer, Udaipur, Ahmedabad, Vadodara, surat and Khedia. 
3. Under the new numbering, it has become part of the NH48.