Question

【题目】There have been no buses _______ half an hour.
A.after
B.for
C.in
D.since

Answer 1

【答案】B
【解析】句意：半个小时没有公共汽车了。for+时间段是现在完成时的标志；since+时间点。因为句子谓语have been是现在完成时，故选B。