题目内容:
Directions: There are 20 incomplete sentences in this section.For each sentence there are 4 choices marked A,B,C and D.Choose the one that best completes the sentence.Mark your answer on the ANSWER SHEET with a single line through the center.It seems 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
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