Correct Option: D

Camels, in ideal conditions, can go 6-7 months without water but as the temperature rises they have to drink water more often. Camels are well known for their humps. They do not, however, literally store water in them as is commonly believed, though they do serve this purpose through roundabout means. Their humps are a reservoir of fatty tissue, while water is stored in their blood. However, when this tissue is metabolised, it is not only a source of energy, but yields through reaction with oxygen from the air 1111 g of water per 1000 g of fat. This allows them to survive without water for about two weeks, and without food for up to a month. Camels are able to withstand changes in body temperature and water consumption that would kill most other animals. Their temperature ranges from 34 °C at night and up to 40 °C during the day. Camels rarely sweat, even when ambient temperatures reach 49 °C. Any sweat that does occur evaporates at the skin level rather than at the surface of their coat, and the heat of vaporization therefore comes from body heat rather than ambient heat. Camels can withstand losing 25% of their body weight to sweating (most mammals can withstand only about 12–14% dehydration before cardiac failure results from circulatory disturbance). A feature of their nostrils is large amounts of water vapor in their exhalations is trapped and returned to their body fluids, thereby reducing the amount of water lost through respiration. The kidneys and intestines of a camel are very efficient at retaining water.