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. The word “complex” in the passage is closest in meaning to? A. extensionB. systemC. regionD. Variety
第二题
……, they tend to build new nests rather than use old, infested ones.On balance, the advantages of colonial nesting clearly outweigh the disadvantages, given the many times at which colonial nesting has evolved independently among different groups of birds. Still lacking, however, is a general framework for testing different hypotheses for the evolution of coloniality. The phrase On balance in the passage is closest in meaning to
A. NeverthelessB. OverallC. ThereforeD. Periodically答案在最 后面哦~