题目

题型：不详难度：来源：

So although Fleming discovered penicillin, it was over a decade ___________someone else turned penicillin into the great drug of the 20th century.

A．when

B．that

C．before

D．unless

答案

C

解析

考查时间状语从句。句意“尽管是弗莱明发现的青霉素，但是青霉素广泛用于药物是几十年后的事情。”it is +一段时间+before意为“过了多久才......”。故选C。