问题补充：
They’re late. The film for half an hour.
A. Has begun
B. has been on
C. started
D. has started
答案：
A. Has begun
(答案→)B. has been on
C. started
D. has started
解析：在现在完成时中，要用延续性动词，与for+一段时间，对于begin和start两个单词都是短暂行动词，必须用be +介词状态表示延续性，故选B
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