【四六级考试网 - 大学英语四六级考试(CET)试题】：
Part II Reading Comprehension (35 minutes)

 

　　Passage One

　　Questions 21 to 25 are based on the following passage:

　　There are desert plants which survive the dry season in the form of inactive seeds. There

　　are aim desert insects which survive as inactive larvae (幼虫). In addition, difficult as it is to

　　believe, there are desert fish which can survive through years of drought (干旱) in the form of

　　inactive eggs. These are the shrimps (小虾) that live in the Mojave Desert, an intensely dry region in the south- west of the United States where shade temperatures of over 50C are often

　　recorded.

　　The eggs of the Mojave shrimps are the size and have the appearance of grains of sand.

　　When sufficient spring rain falls to form a lake, once every two to five years, these eggs hatch

　　(孵化). Then the water is soon filled with millions of tiny shrimps about a millmetre long

　　which feed on tiny plant and animal organisms which also grow in the temporary desert lake.

　　Within a week, the shrimps grow from their original 1 millimetre to a length of about 1.5 centimetres.

　　Throughout the time that the shrimps are rapidly maturing, the water in the lake equally

　　rapidly evaporates. Therefore, for the shrimps it is a race against time. By the twelfth day, how-

　　ever, when they are about 3 centimetre 10ng, hundreds of tiny eggs form on the underbodies of

　　the females. Usually by this time, all that remains of the lake is a large, muddy patch of wet

　　soil. On the thirteenth day and the next, during the final hours of their brief lives, the shrimps

　　lay their eggs in the mud. Then, having ensured that their species will survive, the shrimps die

　　as the last of the water evaporates.

　　If sufficient rain falls the next year to form another lake, the eggs hatch, and once again the

　　shrimps pass rapidly through their cycle of growth,
[page][page], adulthood, egg - laying, and death. Some

　　years there is insufficient rain to form a lake: in this case, the eggs will remain dormant for an-

　　other year, or even longer if necessary. Very, very occasionally, perhaps twice in a hundred

　　years, sufficient rain falls to form a deep lake that lasts a month or more. In this case, the species