中学考试中涉及到的关于代词区别用法有如下这些：
it、one
it是准确指代前文提到的某事物本身（单数）；复数则需要用they（them);在回答what is this? what's that时我们用it代替特殊疑问句中的this和that；在回答what are these？和what are those？时，用they来代替特殊疑问句中的these和those；
one主要用来指代前文提到的某类事物中的一个，也叫泛指用法，其复数用ones，使用one时，其常常带有定语修饰语（前置或者后置 ）
that = the one those= the ones
that与其他几个代词用法还有不同，那就时它可以指代前文提到的不可数名词。
下面是些例子供参考：
I hear that you have bought a new cellphone. May I have a look at it（指前文说的那部手机）?
I lost my pen yesterday when i was playing.I have to buy a new one(指钢笔这类事物中的一支）
This book is a little more difficult than that one/the one on the desk(这里的one指代book)
The weather in Guangzhou is hotter than that in Beijing（that指代前文不可数名词weather）