251. The gyrfalcon, an Arctic bird of prey, has survived a close brush with when the use of DDT was sharply restricted in the early 1970's.
A. extinction; its numbers are now five times greater than
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请问：第一句中的“its numbers are now five times greater than when the use of DDT was sharply restricted in the early 1970's.”
哪两者相比较？
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89. A recent national study of the public schools shows that four years ago.
C. there is now one microcomputer for every thirty-two pupils, four times as many as there were
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第二句中的“there is now one microcomputer for every thirty-two pupils, four times as many as there were four years ago.”
“as many as”后的“there were”是否可以省略而不改变原意，即：
“there is now one microcomputer for every thirty-two pupils, four times as many as four years ago.”
