1.it／one ／that三者均可用作代词,指代前面提到的名词.一般说来,it指代同名同物; one与that则指代同名异物.
I have lost my umbrella; I’m looking for it.（该句中it就是指前面的my umbrella）
I have lost my umbrella; I think I must buy one.（one在该句中表泛指,因为my umbrella已经丢了）
The umbrella you bought is cheaper than that I bought.（替代词that在该句中特指“the umbrella I bought”,以区别“the umbrella you bought”）
2.one与that虽可用来指代同名异物,但one为泛指,相当于a／an＋名词; that为特指,相当于the ＋名词.所以one所指代的名词的修饰语一般为 a／an ／some ／any; that所指代的名词的修饰语往往是the ／this ／that.
A chair made of steel is stronger than one made of wood.（该句中one可以换成a chair）
The water in the cup is hotter than that in the pot.（该句中that可以换成 the water）
3.one只能代替可数名词单数,代替可数名词复数时用ones; that既可以代替不可数名词也可以代替可数名词单数,代替可数名词复数时用 those.I like this pen more than that one.（one代替可数名词单数pen）
There were a few young people and some older ones in the house.（ones代替可数名词复数people）
Mary’s handwriting is far better than that of Peter.（that代替不可数名词 handwriting）
These pictures are more beautiful than those.（those代替可数名词复数 pictures）
4.one既可代替事物,也可代替人,that只能代替事物而不能代替人.有时可以用the one或the ones代替that或those.
The one ／That on the table is mine.（该句中The one代替事物,并且也可以用That）
He is the teacher,the one who is loved by the students.（该句中the one代替人,不能用that）
He advised the farmers to choose the best seed-heads,the ones ／those that had the best color.（该句中the ones代替事物,并且也可以用those）
Cook was a strict but good captain,one who took good care of his sailors.The water in the well is cleaner than that in the river.
It is known to everybody that the moon travels around the earth once every month.
I found it hard to get on with her.
7.it与that均可以替代上文全句的内容或部分内容,而one ／ones则不可以.He has saved my life; I’ll never forget it.（it代替第一分句）
Tom is painting his house.I am told he does it every four years.（it代替前面分句的部分内容painting his house）
Let’s say we meet here at three o’clock.That ought to give you time to buy everything.（That代替前面表述的内容）
1.Mr Zhang gave the textbooks to all the pupils except _____ who had already taken them.
A.the ones B.ones C.some D.the others
2.I find _____ easy enough to get on with Pam.A.that B.this C.one D.it
3.If I can stop her coming to you,I shall do_____.A.those B.which C.these D.it
4.I haven’t a pen.Can you lend me_____?A.these B.those C.them D.one
5._____ is necessary that I get the text of my revision typed.A.There B.This C.That D.It
6.I took _____ for granted that you would stay with us.A.it B.that C.these D.them
7.Few pleasures can equal _____ of a cool drink on a hot day.A.some B.any C.that D.those
8.Of all my old friends,the only _____ I saw much of was Betty.A.it B.that C.one D.this
1. 替代单数可数名词时，三者均可用；替代不可数名词时，不能用 the one，而要用 it 或 that。此时 it 与 that 的区别是：表示同一事物时，用it；表示同类事物时，用 that 或 the one。如：
The weather here is too cold. I don’t like it. 这儿的天气太冷了，我不喜欢这儿的天气。（it 在此指前面提到的 the weather）
The weather of Beijing is colder than that of Guangzhou. 北京的天气比广州冷。（that 在此指代的天气与前面提到的天气为同类）
My uncle bought me a dictionary and I like it very much. 我叔叔给我买了一本词典，我非常喜欢它。（it 在此就是指前面提到的叔叔给我买的词典）
Your dictionary is more useful than the one my uncle gave me. 你这本词典比我叔叔给我的那本词典更有用。（the one 在此表示与前面提到的词典为同类）
2. 替代事物时，三者均可用；替代人时，只能用 the one。如：
—Who is her husband? 哪位是她的丈夫？
—The one by the window. 窗户边的那一位。
3. 当有前置定语修饰时，只能用 the one。如：
—Which do you want? 你想要哪个？
—The red one. 那个红的。
She would rather have the small one than the large one. 她宁愿要小的，不要大的。
4. 当有后置定语修饰时，通常用 the one。如：
My room is better than the one next door. 我的房间比隔壁房间好。
He said he would have the one near him. 他说要靠近他的那一个。
Is that the one that was published recently? 是最近出版的那一种吗?
Here are six rings. Pick out the one you like best. 这里有六枚戒指，选出你最喜欢的一枚。
但是，若后置定语为 of 引起的介词短语，则通常用 that。如：
The population of China is much larger than that of Japan. 中国人口比日本人口多得多。
A grandparent’s job is easier than that of a parent. 祖父母的任务比父母的任务要轻松一些。