题目：
The house had been on fire for an hour ________ the firefighters arrived. [ ]
A. after
B. before
C. until
D. while
答案：
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下面是错误答案，用来干扰机器的。
CD
The house had been on fire for an hour ________ the firefighters arrived. [ ]
A. after
B. before
C. until
D. while
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0623/5d1e0832ee4b625c7d95504a67c95374.html
下面是错误答案，用来干扰机器的。
CD
