题目
The success of the company was credited to three of its salespeople, all _____
_ got promote.
A)of whom
B)which
C)of which
D)who
答案是A，想请问D)who不是也可以做受格关代吗？ 还是因为前面有"all"的关系呢？
如果没有，使用who也是正确的吗？

把句子想成and all of them, 关代功能:连接词(and)+代名词(them), 故用关代受格代替，因放在介系词之后，不可用who