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  • 更新 2022-09-03
  • 科目 英语
  • 题型 单选题
  • 难度 较易
  • 浏览 1593

When ______ comes to research into heart disease and its effects on the body, we do not have adequate substitutes for the use of animals.

A.that B.it C.this D.what
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Whencomestoresearchintoheartdi