Question

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

Answer 1

C

考查時間狀語從句。句意“盡管是弗萊明發現的青霉素，但是青霉素廣泛用于藥物是幾十年后的事情。”it is +一段時間+before意為“過了多久才......”。故選C。