Deserts are found where there is little rainfall or where rain for a whole year falls in only a few weeks' time. Ten inches of rain may be enough for many plants to survive if the rain is spread throughout the year. If it falls within one or two months and the rest of the year is dry, those plants may die and a desert may form.

Sand begins as tiny pieces of rock get smaller and smaller as wind and weather wear them down. Sand dunes(沙丘)are formed as winds move the sand across the desert. Bit by bit,the dunes grow over the years,always moving with the winds and changing the shape. Most of them are only a few feet tall,but they can grow to be several hundred feet high.

  There is,however, much more to a desert than sand. In the deserts of the southwestern United States, cliffs(悬崖)and deep valleys were formed from thick mud that once lay beneath a sea more than millions of years ago. Over the centuries, the water dried up. Wind,sand,rain,heat and cold all wore away at the remaining rocks. The faces of the desert mountains are al?ways changing―very,very slowly―as these forces of nature continue to work on the rock.

  Most deserts have a surprising variety of life. There are plants, animals and insects that have adapted to life in the desert. During the heat of the day,a visitor may see very few signs of living things, but as the air begins to cool in the evening, the desert comes to life. As the sun begins to rise again in the sky,the desert once again becomes quiet and lonely. 

(   ) 1. Where do you often find a desert according to the description of the author?

A.     Where it never rains or snow the whole year.

B.     Where no rivers flow through all the time.

C.     Where you can hardly find any plant and even signs of life.

D.     Where it seldom rains.

(   ) 2. Why does it often take quite a long time for a desert to come into being?

A.     Because the change of climates is very slow.

B.     Because the land is too large to be changed.

C.     Because most deserts come from seas.

D.     Because rocks are hard to be worn down.

(   ) 3. Most living things seemingly tend to be active      

A. in the morning    B. in the afternoon

C. in the evening    D. all day and night

(   ) 4. Which of the following can act as the title of the passage?

A.     How Did the Desert Coming into Being?

B.     All You Should Know of the Dry Land―Desert

C.     The Life around the Mysterious Desert

D.     Desert, the Dead Place for Life

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