替代词that与代词it的用法不同，that用于指代前面提到的“同类”事物，而it主要指代前面提到的“同一”事物。如：
The population of
I’m taking a raincoat with me in case I need it. 我随身带有雨衣，以备不时不需。
■ 替代词those与they的区别
替代词those与代词they用法也不同，those是指代前面提到的“同类”事物，而they (以及宾格them)主要指代前面提到的“同一”事物。如(www.hxen.com)：
Waves of red light are about twice as long as those of blue light. 红色光线的波长约为蓝色波长的两倍。
If the children were to go to the seaside, they would be happy. 如果去海边的话，孩子们会很高兴的。
His books are wonderful. I’ve read every one of them. 他的书写得好极了，我每一本都读过了。