I didn't receive the letter because it _____(send)to the wrong address .顺便解释一下过去完成时是怎么回事!我不怕费事,你也可以发题给我!爱你还有一题，He left home as a young man and ______(not see )since.顺便解释为什么 要不仅要知其然，而且之其所有然的答案！

I didn't receive the letter because it _____(send)to the wrong address .
顺便解释一下过去完成时是怎么回事!我不怕费事,你也可以发题给我!爱你
还有一题，He left home as a young man and ______(not see )since.顺便解释为什么 要不仅要知其然，而且之其所有然的答案！