Without water no living thing can survive, and one feature of the true desert landscape is the absence of vegetation. With little rain and hardly any vegetation the land suffers under the sun. There are virtually no clouds or trees to protect the earth's surface and it can be burning hot. Under the sun, soils break up and crack. Wind and torrential rain sweep away and erode the surface further. Eight million square kilometers of the world's land surface is desert. Throughout history deserts have been expanding and retreating again. Cave paintings show that parts of the Sahara Desert were green and fertile about 10,000 years ago, and even animals like elephants and giraffes roamed the land. Fossil and dunes found in fertile and damp parts of the world show that these areas were once deserts. But now the creation of new desert areas is happening on a colossal scale. Twenty million square kilometers, an area twice the size of Canada, is at a high to very high risk of becoming desert. With a further 1.25 million square kilometers under moderate risk, an area covering 30% of the earth's land surface is desert, becoming desert, or in danger of becoming desert. The rate of growth of deserts is alarming. The world's drylands which are under threat include some of the most important stock-rearing and wheat-growing areas and are the homes of 600--700 million people. These regions are becoming deserts at the rate of more than 58, 000 square kilometers a year or 44 hectares a minute. In North Africa at least 100,000 hectares of cropland am lost each year. At this rate there is a high risk that we will be confined to living on only 50% of this planet's land surface within one more century unless we am able to do something about it.
What does the passage tell us about rainfall in the desert？

A. It never rains.
B. It rains so little that nothing can live.
C. It rains unexpectedly.
D. It rains very infrequently.