In the original test,all the animals

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In the original test,all the animals in a test group are given a substance _______ half of them die

  • A.unless
  • B.until
  • C.lest
  • D.provided

参考答案:

B

本题考查词义辨析。 until:直到。符合句意,表示 given a substance 持续到 half of them die 。