四六级考试

【单选题】 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

网考网参考答案：A
网考网解析：
before用在复合句中，通常强调主句动作发生在从句动作之前，表示“先……再……；先……然后……；而后”，如；All things are difficult before they are easy．诸事先难后易。Before I could understand the first question，the teacher had begun the second one．我还没理解第一个问题，老师已开始讲第二个问题了。 查看试题解析出处>>