Passage 1
An important environment that is more or less totally restricted to the intertropical zone is the coral reef. Coral reefs are found where the ocean water temperature is not less than 21 °C, where there is a firm substratum, and where the seawater is not rendered too dark by excessive amounts of river-borne sediment. They will not grow in very deep water, so a platform within 30 to 40 meters of the surface is a necessary prerequisite for their development. Their physical structure is dominated by the skeletons of corals, which are carnivorous animals living off zooplankton. However, in addition to corals there are enormous quantities of algae, some calcareous, which help to build the reefs. The size of reefs is variable. Some atolls are very large—Kwajelein in the Marshall Islands of the South Pacific is 120 kilometers long and as much as 24 kilometers across-but most are very much smaller, and rise only a few meters above the water. The 2,000 kilometer complex of reefs known as the Great Barrier Reef, which forms a gigantic natural breakwater off the northeast coast of Australia, is by far the greatest coral structure on Earth.
1. According to paragraph 1, all of the following are needed for the growth of coral reefs except? 【否定事实信息题】
A. a solid base to grow on
B. exposure to light
C. the presence of river-borne sediment
D. ocean temperatures of 21 °C or higher
答案：C
解析：原文Coral reefs are found where the ocean water temperature is not less than 21 °C，说明温度不能低于21°C，对应选项D中：21 °C or higher，原文where there is a firm substratum，说明基础一定要坚实，对应选项A中：a solid base，原文the seawater is not rendered too dark，说明不能太暗，对应选项B中：light。过多的沉淀物会遮住光不利于珊瑚礁生长，选项C错在sediment。
2. the word “prerequisite” in the passage is closest in meaning to【词汇题】
A. precaution
B. preparation
C. requirement
D. achievement
答案：C
解析：prerequisite, 先决条件。C选项必要条件，为同义替换，所以C选项正确。
3. According to paragraph 1, algae are important because【事实信息题】
A. they help build coral reefs
B. they are the dominant type of sea life living on the reefs
C. they compete with coral for zooplankton
D. they are an important source of food available to corals
答案：A
解析：原文However, … there are enormous quantities of algae … which help to build the reefs，说明海藻帮助建造珊瑚礁，对应选项A中：they help build coral reefs。
4. The word “complex” in the passage is closest in meaning to? 【词汇题】
A. extension
B. system
C. region
D. variety
答案：B
解析：complex, 复合体。B选项系统，为同义替换，所以B选项正确。
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