为什么用that不用those?指代的不是复数吗？

Question

By the middle of the 20th century scientists believed they were well on the way to treating,preventing,or eradicating many of the deadly infectious diseases that had plagued humankind for centuries.

Answer 1

that：那个
those：哪些
that是those的单数，those是that的复数形式
如：That is my friend.那个是我的朋友。（一个人）
Those are my friends.哪些是我的朋友。（多个人）

Answer 2

that had plagued humankind for centuries 是一个定语从句，修饰diseases。that 叫做关系代词，它代替diseases 在定语从句中作主语。它可以代替复数名词，也可以代替单数名词，还可以代替不可数名词。追答

diseases that had plagued humankind for centuries 汉义:困扰人类好多世纪的疾病

谢谢啦

本回答被提问者采纳

Answer 3

他们说的都不对啊，这里必须用that，你这个句子是定语从句主语从句啊。这里不是代词的问题，是定语从句。

Answer 4

因为前面的deadly infectious diseases指是infectious这一类疾病，并非数字意义上的复数。

Answer 5

因为前面是clothes，复数，这里的those指代前面提到过的可数名词复数，指代同类事物追问

亲 题目不一样