请教一道关于英语成分的问题（定语从句中）？

Question

The doctor__________is going to Europe next year.
A.which the manager is talking to
B.who the manager is talking
C.the manager is talking to him
D.the manager is talking to
材料的答案是D，但是我对这句句子的句子成分不是很清楚，不知道D选项中省略了什么关系词，我认为这个短语是做“the doctor”的定语，可是……请教知情者，谢谢

Answer 1

原句是：the doctor whom（who，that）the manager is talking to is going to Europe next year。这是个定语从句，先行词是doctor，that作宾语时可省略。如the boy i wrote to is Tom。

Answer 2

是的 D中的Who因为在定语从句中做宾语所以省略(The manager is talking to the doctor)