问题
选择题
While they ________ the bus, an old man fell to the ground. [ ]
A. are waiting for
B. wait for
C. will wait for
D. were waiting for
答案
答案：D
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While they ________ the bus, an old man fell to the ground. [ ]
A. are waiting for
B. wait for
C. will wait for
D. were waiting for
答案：D