Scientists say it may be ten years _____ this medicine was put to_英语解答

Scientists say it may be ten years _____ this medicine was put to use.
A since B before C after D.when
给出正确答案,理由和翻译

人气：474 ℃　时间：2020-06-15 04:33:13

解答

选B.
后面的宾语是一个从句,before引导的时间状语从句,before this medicine was put to use 这种药物投入使用之前.
Scientists say it may be ten years when this medicine was put to use.
整句话意思是
科学家说10年后这种药物才能投入使用.