问题描述：
"why couldn't they meet us at five o'clock?"
"Because they were delayed by ___"
A.a heavy traffic B.heavy traffic C.some heavy traffic D.traffic being heavy
答案是B 不知道为什么
"Because they were delayed by ___"
A.a heavy traffic B.heavy traffic C.some heavy traffic D.traffic being heavy
答案是B 不知道为什么
问题解答：
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