Question

为什么不能用that, 它不是可以指人吗?

Among the 250 million people _______ get sick because of water pollution, 5 to 10 million of them die.
A. that B.which C. whose D. who

Answer 1

当关系代词指人时，关系代词既可用who，也可以用that。但在以下情况用who。
1.当先行词是persons, people, those时。

2.当先行词是he, one, all, any, they等时，例如：
He who has not reached the Great Wall isn't a true man. 不到长城非好汉。

3.在非限定性定语从句中用who。

4.在强调句型中多用who，在口语中who可以省略。
It is he who can do this work. 只有他能够干此工作。

所以选 D

Answer 2

后面有个because 用that就不通顺了，

因为后面5 to 10 million of them die是指在前面250million中死去的人 所以应该选d。