翻译：____________________ what had happened.
1.It took a long time for him to find what had happed.
2.It was a long time before he found what had happened.
3. It had been a long time before he found what had happened.
4. After a long time, then he found what had happened.
请教专家老师们，以上翻译是不是正确？特别是第3和4句，was 和had been 是不是正确，为何？我感觉不是更应该用had been 吗？
第二，老师们有什么其他的翻译句型，期望补充给大家学习。 很感谢。
1. It took a long time for him to find what had happed.
2. It was a long time before he found what had happened.
3. It had been a long time before he found what had happened.
4. After a long time, then he found what had happened.
我感觉第前面两句挺好的，后面两句不怎么样。
第3句的主句用过去完成时不怎么样，由于这个主句的时态是与从句 found 的时态直接有关，虽然从句意来看，主句谓语发生在从句谓语之前，但因为 before 在词义上已体现了其先后关系，所以主句不必须要再用过去完成时，特别是，假如主句用了过去完成时，则与 found 后面的从句中所用的过去完成时相重复，且没办法体现其先后关系。本句的时间先后顺序为：发生某状况——过了很久——他发现了。
第4句本来挺好的，但用上 then 就不好了，由于其前只是一个介词短语，不是一个表示动作的句子。假如去掉 then，本句挺好的。
其他的翻译举一例：
Much later on,he found what had happened.
或者把前面两句中的 a long time 改成 ages 也可以。
