The succulent stem of the cactus plants usually store water and carry out photosynthesis also. The cactus stem contains a tough and waxy outer layer, called cuticle. The cactus plants possess modified leaves shaped like thin spines or thorns that decrease water loss through transpiration. 

Stomata in xerophytes open in night and remain close during day to prevent loss of water through transpiration.

"Patther phul" or stone flower or rock moss is a xerophytic plant or xerophytic shrub occurring wild on rocky ground( not much water present) As it is a plant which needs very little water it is called a xerophyte and occurs in the region of Gujarat 

One of the most commonly found plants in deserts is opuntia. it is a type of cactus. It is also called prickly pear. It is used to treat burns, diabetes, ulcers, inflammation, etc.

Xerophytes have very small leaves or spines to reduce loss of water.

The osmotic concentration of cell sap is higher in xerophytes to allow them to absorb water in an otherwise water deficient environment. The higher osmotic concentration would mean a lower water potential. A lower water potential will be advantageous to xerophytes as water always flows from a higher water potential to lower water potential.

Most species of desert plants have lost true leaves, retaining only spines, which are highly modified leaves. As well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of leaves, enlarged stems carry out photosynthesis.

The cuticle is a waxy coating over the surface of leaves and plants. It forms a waterproof coating over the surface of leaves and plants. It prevents water loss from plants and also prevents the plants from getting desiccated. It also prevents the intake of gases into the plants. 

In cacti, the succulence is mostly in the stems because the leaves of the cacti are reduced to thrones to minimize the surface areas and therefor the water evaporation through them. the cacti have a shallow widespread network of roots that enables them to absorb water, therefore the roots are not succulent. the cacti have thick stems that store maximum amount of water in the entire plant. So, the correct answer is 'Stem'.

A phreatophyte is a deep-rooted plant that obtains a significant portion of the water that it needs from the phreatic zone (zone of saturation) or the capillary fringe above the phreatic zone. Phreatophytes are plants that are supplied with surface water and often have their roots constantly in touch with moisture. These plants have very deep roots that are able to reach the water table. So the correct answer is ' Very deep reaching ground water fringe'. 

The xerophytic plants are the plants present in the desert and other dry environments. The rate of transpiration is high in xerophytic plants due to high temperatures. In order to minimize the rate of transpiration, they have sunken stomata.

Lamina is reduced in xerophytic plants. In xerophytes, the petiole is modified into expanded green structure which carries out photosynthesis in case of reduced lamina.  For example, in Australian acacia.

Xerophytes are the plants that survive in an environment having little supply of water or moisture. To survive with limited water supply they have anatomical modifications such as-

In non-succulent Perennial have extensive root systems, roots penetrate deep into the soil and establish contact with sub-soil water. 

• Some trees have deep, extensive root systems that anchor them to hillsides. Shrubs service berry is a deep-rooted deciduous shrub or small tree that grows best in well-drained, slightly acidic, moist soil. Ground covers, Vetiver Grass.

Acacia arabica is xerophyte because it is seen in desert places.

Xerophytes are made up of thick cuticles and contains parenchymal tissues. It does not contain Aerenchyma.

• Water storage in stem and tubers is an adaptation of plants to thrive in harsh environments with high temperatures and scarce water. Such plants called xerophytes usually develop succulent stems that can store water.
• They have a very extensive root system to absorb the maximum amount of water from the soil.
• Other adaptations include thick waxy cuticle, reduced leaf size, densely packed leaves, reduced number of stomata in pitted and grooved positions.

Vegetation of geographic region with low rainfall, high temperature, loose and sandy soil is of the type called xerophytic vegetation. It consists of spiny shrub, cactus. Caatinga is a type of xerophytic vegetation.

A xerophyte is the species of plants, that has the special characters to adapt in the environment with little water. Xerophytes plant have a thick waxy cuticle on the stem and leaves. This waxy cuticle reduces the water evaporation. In xerophytic plants, sunken stomata are present. which open during the night to prevent the water loss. To adapt in this environment, xerophytic plants leaves reduces into spines, which reduces the surface area of the leaf and reduces the amount of transpiration. The xerophytic plant makes their food through the CAM pathway.

Lithops (stone-faced as the plants appear stone-like)  is a genus of succulent plants in the ice plant family, Aizoaceae. They avoid being eaten by blending in with surrounding rocks and are often known as pebble plants or living stones. These are small succulent plants that survive in their harsh environment by having much of the plant body below ground. Each individual plant consists of two succulent leaves fused together in the shape of an inverted cone (although some species will produce multi-headed plants). The fissure at the top of the plant is the division between the two leaves and is spine-like. 

Vegetation of Rajasthan is xerophytic. It is a geographic region with low rainfall, high temperature, loose and sandy soil. It consists of spiny shrub, cactus. Caatinga is a type of xerophytic vegetation.

Hence, option A is correct.

The trees having a height 15 m and above have strong buttresses at their base. Buttresses are modified roots appear from the basal parts of main stem and spread in different directions in the soil, eg, Ficus, Bombax, etc. Thus the correct answer is option B.

Various organisms, if unable to migrate, might avoid the unfavorable environment by escaping in time. Polar bears go into hibernation during winter seasons to escape extreme cold. Some snails and fish undergo aestivastion to avoid summer-related problems like heat and desiccation, etc. 

As the altitude increases, the atmospheric pressure decreases. Thus reducing the level of oxygen. People living at higher altitudes are used to the lower density of oxygen molecules in the air. They have higher levels of haemoglobin (red blood cells) in their blood which helps them to take in more oxygen. In contrast, people living at lower altitudes have lesser haemoglobin concentrations as they experience a higher density of oxygen molecules in the air.

There are various causes of biodiversity losses. One of the reason is habitat loss and fragmentation. When large habitats are broken up into small fragments due to various human activities, mammals and birds requiring large territories and animals with migratory habits are badly affected. This results in the decline in their population.

Lithops plants or Pebble plant consist of one or more pairs of bulbous, almost fused leaves opposite to each other and hardly any stem. The slit between the leaves contains the meristem and produces flowers and new leaves. The leaves of Lithops are mostly buried below the surface of the soil, with a partially or completely translucent top surface known as a leaf window which allows light to enter the interior of the leaves for photosynthesis. 

Bears usually go into hibernation (a) during winter to escape (b) cold weather. (Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy that is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate.)

In the conditions of water scarcity, the frogs show biological adaptation to reduce water loss or obtain water from the surroundings. The skin is modified to contain water channels. The water is absorbed from the surroundings through the skin and the water channels makes the water available for the survival.