It still puzzles today's scientists _____ some mammals produce their young _____ others lay eggs to producetheir offspring (后代).

试卷相关题目

• 1'Sorry, sorry...', he whispered, _____ talking to himself.

  A.while

  B.even if

  C.as if

  D.when

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• 2They will come to help us with the harvest _____ they are busy tomorrow.

  A.even if

  B.however

  C.as though

  D.even although

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• 3It is considered by some people that to pay to see a movie will be foolish ____ you can see it on TV for nothing.

  A.where

  B.when

  C.however

  D.that

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• 4He found it increasingly difficult, _____ his eyesight was beginning to fail.

  A.though

  B.for

  C.but

  D.so

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• 5At first he hated the new job but decided to give himself a few months to see _____ it got any better.

  A.when

  B.how

  C.why

  D.if

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