问题
选择题
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
答案
答案：D
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。