John waited at the bus-stop for nearly half an hour the bus finally arrived .A.w
来源：网络
时间：
推荐文章
John waited at the bus-stop for nearly half an hour _____ the bus finally arrived .
A.when
B.as
C.before
D.while
试题答案
C
before引导时间状语从句，公共汽车来之前，我已等了将近半个小时了。故选C。