Complete the sentence: The new drug must undergo rigorous trials ____ it can be approved for public use.

  • A. before
  • B. after
  • C. unless
  • D. although

Explanation

Trials logically precede approval, so before is the only connector that puts the two events in the right order. After reverses the sequence and unless would make approval the default. Time relationships are as much a part of these questions as meaning.

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