It seems that oil from this pipe for some time.We’ll have to take the machine apart to put it right.
A. had leaked
B. is leaking
C. leaked
D. has been leaking
网友回答
A. had leaked
B. is leaking
C. leaked
(答案→)D. has been leaking
解析：考查时态。现在完成进行时表示从过去一直延续到现在的动作，而且此动作还有可能延续下去。