Oceans cover nearly 75% of the earth's surface.based on the amount of light received，the ocean can be divided from its surface to its depth into three zones.Sunlit zone is the top layer，which goes down about 600 feet.There is rich light going through the water for photosynthesis to occur here.More than 90% of all marine life lives in the sunlit zone.

Twilight zone begins at about 600 feet under the water and extends to the darkest part，which begins about 3，000 feet down.only a small amount of light can reach the water at this depth.As the water becomes deeper，the water pressure increases，too.Plants do not grow here.Some animals that live in the twilight zone can use their bodies to make light.90% of the ocean is in the midnight zone.It is entirely dark—there is no light.The water pressure is extreme.The temperature is near freezing.What can live in the midnight zone？The living things found here live close to cracks in the earth's crust.These cracks give off mineral-rich materials from the earth itself.Special forms of bacteria use these materials from the cracks for energy to make food.All other living things are nourished by these bacteria.

Living things in oceans have always been an important and reliable source of food.Ocean fishing accounts for 80% of the world fish catch.However，overuse of the ocean by man has led to the decline in population of some fish.Therefore，overfishing should be studied as a real problem in future scientific exploration.

（  ）1.According to the passage，three zones of the ocean have the following differences EXCEPT_____.

A.the pressure of water

B.the depth of water

C.the influence of fishing

D.the amount of light

1.C【解析】细节理解题。根据第一段第二句“based on the amount of light received，the ocean can be divided from its surface to its depth into three zones.”和第二段第三句“As the water becomes deeper，the water pressure increases，too.”可知，根据接收到的光量，海洋在深度上可分为3个区域，且随着水体深度的增加，水压也随之增加。故选C。

（  ）2.Most living things in the midnight zone depend directly on_____to live.

A.cracks

B.mineral

C.the earth’s crust

D.special forms of bacteria

2.D【解析】细节理解题。根据第二段最后一句“All other living things are nourished by these bacteria.”可知，所有其他生物都以这些细菌为生。故选D。

（  ）3.Which of the following statements is NOT true according to the passage？

A.There is no plant in twilight zone due to the increase of water pressure.

B.From midnight to sunlit zones，the water pressure decrease.

C.Some marine lives could exist with no light.

D.Darkness covers most of the ocean.

3.C【解析】细节理解题。根据第二段第四句“Some animals that live in the twilight zone can use their bodies to make light.”可知，有些生活在边缘地带的动物自身可以发光，但并未提到可以在没有光线的环境中生存。故选C。

（  ）4.What is the main topic discussed in the passage？

A.The relationship between the ocean and the earth’s surface.

B.The division of the ocean’s layers.

C.The living condition of marine lives.

D.The overuse of the ocean.

4.B【解析】主旨大意题。文章开篇根据海水深度及其光照情况将海洋进行分层，接下来依次描述了各层的情况。故选B。