问题补充：
How can I ever concentrate if you continually me with silly questions?
A. have…interrupted
B. had interrupted
C. are…interrupting
D. were…interrupting
答案：
A. have…interrupted
B. had interrupted
(答案→)C. are…interrupting
D. were…interrupting
解析：因为从can和句意可知，是指目前正在发生的事。句意是“如果你 (象现在这样) 不断地用一些无聊问题来妨碍我，我又怎能集中精力呢？”
