B. Read the passage carefully, then choose the correct answers.

A desert is a region where only special forms of life can exist because there is a shortage of moisture.

Most of the dry, hot deserts with which we are familiar are found in two belts around the world, just north and south of the Equator. They are caused by high atmospheric pressures that exist in those areas which prevent rain from falling. Other deserts, which are found farther away from the Equator, are the result of being in ‘the rain shadow’.

Deserts differ greatly in appearance. Where sand is abundant, the winds may build sand hills or dunes. These are sand deserts. Rock deserts consist mostly of bare rock, which forms fantastic cliffs and hills. No great rivers originate in deserts. But a river may rise in moist areas and cross great deserts on its way to the se  a. The Nile, for example, flows through the desert region of the Sahar  a.

The animals that exist in the desert are those that have managed to adapt themselves to its conditions. They must be able to do without water for long periods, or be able to reach water holes at great distances. The camel, for example, is highly adapted to desert life. It has padded feet to walk on sand, a water-storing stomach, humps of fat as a reserve supply of energy, and nostrils that can be closed to keep out sand during windstorms. Many of the smaller desert creatures need to drink no water at all. They get what liquid they need from the sap of food plants and from night dew on leaves or stones.

According to the passage, a desert is a region where _______ .