Read the passage carefully and answer the given question: A desert is…

Read the passage carefully and answer the given question:
A desert is basically a wilderness or a wasteland. There is little moisture and poor soil such as sand, gravel or rock. There are few plants to offer shade. Deserts can be described as harsh places. Many are burning hot by day and cold by night.

Every continent has deserts. Much of the western United States is a desert. A desert region called The Outback covers Central Australia. The southern tip of South America is largely desert. Northern Africa is covered by the Sahara, a desert as big as the mainland United States. The Arabian Peninsula, between the Persian Gulf and the Red Sea, is almost entirely desert. A large part of central Asia, from China to the Caspian Sea, is mostly desert. Deserts cover 1/8 of our planet.

The popular belief is that a desert is dry, hot, waterless and without shelter. But this is not entirely correct. For those who have studied it, the desert can be a beautiful place. It is home to a variety of people, animals and plants that have learnt to live under hot and dry conditions. A desert is not always a flat, unchanging wasteland of dry sand. It may have mountains and hills. It may have an oasis, big or small. An oasis is like a green island in the middle of a desert where a spring or a well gives plants and trees a better chance to grow.

All living things need water in order to survive. The few plants and animals that live in deserts have developed the ability to require less water than most plants and animals. Desert plants have adapted to heat and dryness of the desert. Plants such as cacti have special means of storing and conserving water. They often have few or no leaves. Some plants have gotten used to arid environments by growing extremely long roots, allowing them to acquire moisture at or by the water table.

The desert animals also have found a way to solve the heat and water problems the desert environment creates. Camels can drink a lot of water at one time. They can live without water for days together. The reason is they sweat very little. We sweat because we must keep our body temperature constant. We sweat when it gets hot, and this cools the body. Camels can stand a high body temperature. They don't need to sweat and can therefore retain the water they drink for long periods of time.

Q. Certain plants are able to survive in deserts because they: