第17题: [单项选择]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 参考答案:A 答案解析:“It's... before”句型表示“(……之后)才……”之意。until直到……为止.在否定句中多译为直到……才,该词一般不用在it is...until肯定)句型中。It is (has be