A man escaped from the prison last night. It was a long time the guards discover
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A man escaped from the prison last night. It was a long time ________ the guards discovered what had happened.
A.before
B.until
C.since
D.when
试题答案
C
解析：本题要突破定向思维，不是It was a long time before句型，注意空格后面的时态是过去完成时，前面是过去时，因此从时间概念上看应该是since．