Enrico Fermi (1901-1954) was an Italian physicist and recipient of the 1938 Nobel Prize in Physics. He created the world's first nuclear reactor, the Chicago Pile- 1.

CH$ _4$ is methane, which is the major component of biogas. Ratio is 3:1. 

Biogas typically refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste or food waste. It is a renewable energy source.
Biogas can be produced by anaerobic digestion with anaerobic bacteria, which digest material inside a closed system, or fermentation of biodegradable materials.

Energy plantation is the method in which there is the cultivation of certain species of the plants which can be used as the source of energy. They can be used as an alternative to the fossil fuels. This reduces the pressure on the fossil fuels. 

Anaerobic digestion is a natural process in which bacteria convert organic materials into biogas. It occurs in marshes and wetlands and in the digestive tract of ruminants. The bacteria are also active in landfills, where they are the principal process degrading landfilled food wastes and other 
biomass. Biogas can be collected and used as a potential energy resource. The process occurs in an anaerobic (oxygen-free) environment through the activities of acid- and methane-forming (methanogenic) bacteria that break down the organic material and produce methane and carbon dioxide in a gaseous form, known as biogas. 

The Wind is an inexhaustible source of energy. Asia's largest windmill or wind farm complex is established at Lamba village in the Jamnagar district of Gujrat. It had successfully generated 1500+ kWh in its pilot stage of 3 months. Thus the correct answer is option B.

The device which can trap the solar energy and convert the solar energy into an electrical form of energy is called as the solar cell. Solar cells are generally used for the storage of the radiations from the sun in the form of energy resource. These cells are used in the solar panels for the generation of electricity for the street lights. 

Thermal pollution is caused by change in water temperature which leads to degradation of water quality. It is caused due to use of water as a coolant by power plants and industrial manufacturers. When such water is returned to the natural environment at a higher temperature, it decreases oxygen supply and affects ecosystem composition.

Netherland is referred as the land of the windmills. There are many windmills installed in the regions called as wind farms. There are large turbines which are used for the conversion of the wind energy to produce electricity. About 3400 MW energy was produced in this region with the help of windmills.

In a biogas plant, household wastes and biowastes can be disposed of usefully and in a healthy manner to obtain biogas a renewable source of energy, which is used as a fuel because it reacts with oxygen and  releases energy, which is clean in nature. Also the residue of the plant can be used as a manure.

Wind energy is an inexhaustible energy resource which has been used for centuries to ran wind mills and pump water.

In some places, the hot water comes to the earth surface as hot spring which can be used to generate electricity. In Himachal Pradesh, electricity is generated by this method.

• Biomass is the amount of organic matter present in an organism at a given time. It is the stored form of energy in an organism.
• Biofuel is any substance which has a biological origin and can be used as a fuel. For example, fuel wood.
  
• Biogas is formed from the decomposition of organic matter and can be used as an alternative source of energy in place of fossil fuels.

• Methane 50- 75%
• Carbon dioxide 25- 35%
• Hydrogen 0 -1%

• Methane 50- 75%
• Carbon dioxide 25- 35%
• Hydrogen 0 -1%

coal, oil & organic compounds contain carbon as the main constituent thus they can evolve carbon dioxide, while nuclear energy will release no carbon dioxide.

Biogas is a type of fuel. It is a mixture of different gases produced when organic matter breaks down in the absence of oxygen. The organic wastes release many gases primarily methane and carbon-dioxide. It is produced by anaerobic fermentation. It is counted as eco-friendly gas.

Biogas refers to a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen. Biogas is produced by anaerobic digestion with methanogen or anaerobic organisms, which digest material inside a closed system or fermentation of biodegradable materials. There are two key processes: mesophilic and thermophilic digestion which is dependent on temperature. Research in biogas production indicates that the optimal temperature for mesophilic bacteria is around 37°C and around 55°C for thermophilic bacteria.

 Electricity in its natural form is from lightening. Various natural resources like wind (wind mills), water (turbines), fossil fuels are used to produce electricity. Therefore, electricity is a product obtained using natural resource and its since natural form cannot be easily harnessed  so cannot be nither classified as a natural resource nor a man made product.

Biogas is a mixture of methane, carbon dioxide and other trace gases which can be converted to heat, electricity or light. Small-scale biogas reactors are designed to produce biogas at the household or community level in rural areas. 

Eichhornia crassipes is an excellent source of biomass because of its extremely high rate of development. One hectare of standing crop thus produce more than 70,000 m$^3$ of biogas.

Sun derives the water cycle, heats up water in ocean and seas, and then water vapours evaporate to air. As the vapours move upward the cool temperature there causes it to condense into clouds and they fall as precipitate like rain, hailstone etc.

The economics of terrestrial growth of vegetation for its energy content is far more favourable than other more technically sophisticated methods of large-scale solar energy conversion. The most traditional is to use the ability of plants to convert the suns energy into fuel molecules; this is cheap, deployable at scale, and provides the energy in easily storable form, but its not very efficient and so needs a lot of land.

Biogas (gobar gas) is primarily methane (CH$ _4$) and carbon dioxide (CO$ _2$) and may have small amounts of hydrogen sulphide (H$ _2$S), moisture and siloxanes.

Biogas consists mostly of methane (CH$ _4$), carbon dioxide (CO$ _2$) and a mix of trace gases including nitrogen, hydrogen sulfide (H$ _2$S), hydrogen and others. Methane is the main constituent (63%) of the biogas. The other major constituent is CO$ _2$ (30%).

Material recovery is possible from industrial waste. Organic waste can be used for energy production with various processes such as bio-gas production.

Solar energy is considered to be the non-conventional because it is not derived from the conventional fossil fuels. It is inexhaustible as it will not be used up completely. It will not take much time in regeneration. It is universal as most of the places on earth that sustain a large population get the sunlight. Wind energy is also non-conventional and inexhaustible but it is not available to every area. It can be harnessed in areas that witness a low pressure, like equatorial and tropical areas. Similarly, the tidal energy is available to the coastal areas. Hydrothermal resources are available everywhere but need a heavy economic investment for their usage.

Photovoltaic cells are used in trapping solar energy. These are made of semiconductors that can lose the electrons when exposed to the sunlight to generate the electric current. The semiconductor material used can be silicon, gallium arsenide, cadmium telluride. Silicon is the most preferred because of its uniform crystalline structure. Cadmium Telluride provides a low-cost alternative that is also highly absorptive of solar energy. Gallium arsenide is used for its resistance to the harmful effects of the radiations. It is generally used for space photovoltaic cells.

Solar energy can be trapped through the following:

At the later stages of decomposition of cowdung, mesophilic micro-organisms decompose the dung, generating heat from exothermic( process which produces heat) processes; such heat generation is associated with the well known phenomenon of the elevated temperature of composting.