Question

 John waited at the bus-stop for nearly half an hour _____ the bus finally arrived .

         A. when B. as        C. before         D. while

Answer 1

C

解析:

before引導(dǎo)時(shí)間狀語(yǔ)從句，公共汽車來之前，我已等了將近半個(gè)小時(shí)了。故選C。