阅读理解D
The deserts of the world are not all covered with sand. Many of them have surfaces of rock or clay(黏土) or small stones. They are not flat, either. They often have high hills and deep valleys. There is some plants’ life in many parts of the desert. There is little rain in the desert, but it does fall often enough for most plants.
The deserts of the world are not uninhabited(无人居住的). People also live outside oases(绿洲), but these people are not farmers. They have camels, goats, donkeys, sheep, etc. These animals can live on the desert plants and do not need much water.
The people of the desert have to move constantly from place to place, they must always look for grass or desert plants for their animals. They usually live in tents. When there is no more food for their animals, they fold up their tents, put them on their camels and donkeys, and move to another place. In good years, when there is enough food for their animals, they trade their skins and their goats and camel hairs with the people of oases for wheat and fruit. But in bad years, when there is not enough food for their animals, the people of the desert would attack the oases people. But they are also hospitable, no man in the desert would ever refuse to give a stranger food and water.
According to the passage, deserts are mostly made up of ________.

A．clay

B．rock

C．stones

D．sand

The underlined word “hospitable” has the meaning of being ________.

A．kind

B．brave

C．cruel

D．strange

In the desert ________.

A．It rains in spring only.

B．it rains for a short time every month

C．the rainfall is just enough for the plants

D．there is some rain, but far from enough

People live ______.

A．only inside the oases	B．both inside and outside the oases
C．only outside the oases	D．in places with regular rainfalls.