The correct option is
A Both the assertion and reason are true and the reason is the correct explanation of the assertion
Deserts are terrestrial biomes that are characterized by an extremely arid climate. They receive least rainfall (less than 50 centimeters of rainfall annually) and have extreme high temperatures with conditions like low atmospheric humidity (the amount of water vapour in the atmosphere).
The soil is sandy, gravelly or stony and can not hold water. These areas or biomes have sparse vegetation, deep rooted shrubs, succulent xerophytes. For example, Thar and Sahara desert. Hence reason is a true statement.
Desert vegetation and animals have various adaptations to survive in these harsh conditions. For example, desert plants such as cactus (Opuntia) have enlarged fleshy stems (phylloclade) to store water and perform photosynthesis. The leaves are reduced to spines to prevent loss of water in the form of water vapour through stomata (transpiration).
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1339607/original_opuntia.png)
Figure : Opuntia
Desert animals such as the camel sweat less and urinate less frequently to conserve water. Hence, both the assertion and reason are true and the reason is the correct explanation of the assertion.
![](https://df0b18phdhzpx.cloudfront.net/ckeditor_assets/pictures/1339626/original_Desert_biome.png)
Figure : Desert biome with cactus and camel