Question

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

       A．when       B．a(chǎn)s     C．before      D．while

Answer 1

C

解析:

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