Much more research is needed _______ scientist find a drug that can safely provide the same effect on man.A.where B.that C.until D.before为什么不选C

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Much more research is needed _______ scientist find a drug that can safely provide the same effect on man.A.where B.that C.until D.before为什么不选C
Much more research is needed _______ scientist find a drug that can safely provide the same effect on man.
A.where B.that C.until D.before
为什么不选C

Much more research is needed _______ scientist find a drug that can safely provide the same effect on man.A.where B.that C.until D.before为什么不选C
Until 在它意思为:在.之前,直到..才 的时候,常用语否定句中
He did not set foot in England again until 2002.
直到2002年他才再次来到英国踢球

until 要于not 连用构成not until 的句型,意思是在什么什么之前我们不能怎么怎么去做。

before 指的是时间限制
而until指的是药发明出来后就不需要研究

简单解释,这句话的意思是在科学家发现这种药能安全用于人 ( 之前 before ),需要更多的研究。