one it that those的区别和用法详解：
one, it, that和those可代替上文提过的名词，以避免重复。
它们的用法，最主要的区别如下：

it ：特指之前提到的同一个事物
（特指同物）

one：泛指之前提到的同类中的任一个人或物
（泛指同类不同物）

that：特指前文提到的同类中的特定的事物 
（特指同类不同物）

（泛指：不明确指定；特指：明确指定）

1.it：特指同物
This pencil is mine. You can have it.
这只铅笔是我的。你可以拥有它。
（it 特指上文提到的同一只铅笔。） 

 复数意义，用they/them。
These pencils are mine. You can have them.
这些铅笔是我的。你可以拥有它们。


2. one：泛指同类不同物
My pencil is broken. Can you lend me one?
我的铅笔破了。你能借给我一只（铅笔）吗？
one泛指任一只铅笔 

He couldn't find his bag. So he bought a new one.
他找不到他的书包。所以他买了一个新的。
one泛指一个书包，未明确是哪个

复数意义，用ones
I don’t like big apples. I like smaller ones.
我不喜欢大苹果。我喜欢小苹果。
ones泛指apples，未明确是哪些苹果


3.that：特指同类不同物
The weather in Hainan is better than that in Guangzhou.
海南的天气比广州的好。
that = the weather, 特指（广州的）天气

The window is bigger than that by the door.
这个窗户比门边的那个窗户大。
that= the window，特指（门边）的那个窗户 

复数意义，用those

The windows are bigger than those by the door.
这些窗户比门边的那些窗户大。
those = the windows，特指（门边）的那些窗户

TIPS:
从例句中可发现：
1）that/those 常后接修饰语，以体现特指。
比如：
The windows are bigger than those by the door.
 （特指是门旁边的那些 ）

此时：
that(指代可数名词单数) + 修饰语 = the one +修饰语
those (指代可数名词复数) + 修饰语 = the ones+修饰语

The window is bigger than that by the door.
= The window is bigger than the one by the door.

The windows are bigger than those by the door.
= The windows are bigger than the ones by the door.

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附：随机初级英语语法基础题
1. Thanks for your invitation, but I’m so sorry I can’t go. I need to ________ my baby at home.
   A. take away           B. take off              C. take care of      D. take out of 
take away 拿走，take off脱掉、起飞，take care of 照顾，take out of 取出。原文表示照顾婴儿，故选C。
结语：one it that those 的区别，需要细细斟酌才能更好的理解它们的用法。