Question

Mr.Smith saw the empty seat next to me and asked____.为什么选D

Answer 1

朋友，你一个选项也没给

不过，根据你的句子，我可以猜一下

Mr. Smith saw the empty seat next to me and asked (whether it was taken).
或
Mr. Smith saw the empty seat next to me and asked (whether he could sit there).
Mr. Smith saw the empty seat next to me and asked (whether it was available).
这些都是可能的，如果你把选项给出来，就可以帮你分析一下为什么一定要用这个D

在百度上查了一下
A.where has Jeff gone B.where did Jeff go
C.where Jeff has been D.where Jeff had gone
如果你问的是同一个问题，从前文分析，这个Mr. Smith一定是个老师，看到我身边的座位空着，就问杰夫去哪儿了，显然Jeff不在是先于老师发现他座位空着而发生，因此要用过去完成时态
A现在完成时 B过去时态
C现在完成时（这个说明此人已经回来了）

Answer 2

Because “where Jeff had gone”suggests that Jeff Jeff had gone before Mr.Smith came. So it's a past in the past.