题目内容
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
B
解析:
略
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题目内容
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
B
略