the pen I thought I had lost is on my desk

题目

the pen I thought I had lost is on my desk
为什么用had lost 的呢?哪位大侠知道的

答案

因为前面的动词是thought,过去认为笔丢了,要强调对现在造成的影响.
过去的过去,所以使用过去完成时,即：had lost