One替代前面出現的「同名異物」的可數名詞單數，表示同類事物中的「一」，相當於「a/an+可數名詞單數」，表示泛指概念，其複數形式是ones。
Two years ago she bought an expensive mountain bike and then she persuaded me to buy one.
兩年前她買了一輛昂貴的山地車，然後她說服我也買了一輛。
Its color is blues; I want a red one.
它是藍色的；我想要個紅色的。
I hope there are enough books for each students to have one.
我希望有足夠的書，可供每個學生一人一本。
I don』t like red apples, I like green ones.
我不喜歡紅蘋果，我喜歡綠色的。
We should not only love new friends, and forget old ones.
我們不能只愛新朋友，忘記老朋友。
the one特指前面出現的可數名詞單數（有時可用that替代），其複數形式是the ones(有時可用those).
The problems now are different from the ones/those that we were faced with last year.
現在的問題與我們去年面臨的不同。
You must clean this room and the one upstairs.
你必須打掃這個房間，還有樓上的那個房間。
that替代前面提到的「同名異物」的可數名詞單數或不可數名詞，相當於「the +可數名詞單數/不可數名詞」。
The weather here is colder than that in China.
這兒的天氣比中國的冷。
those替代前面替代的「同名異物」的可數名詞複數，是特指，也可看作that的複數形式。
The books are better than those on the shelf.
這些書比書架上的那些好。
it替代上文提到的用一事物，替代的通常是可數名詞單數或不可數名詞，通常用作形式主語、形式賓語。
He bought a book and lent it to me.
他買了一本書，借給了我。
We all find it strange that the little child can』t speak at all.
我們很奇怪地發現這個小孩不會說話。
習題
一選擇題
1 --I saw no more than one motor car in that shop. Will you go and buy one?4
-No, I』d rather find _____ in other shops.
A one, one B. it, one C. one, it D. it, it
2. ______ felt funny watching myself on TV.
A. One B. This C. It D. That
It作形式主語
3. He didn』t make ___ clear when and where the meeting would be held.
A. this B. that C. it D. these
4. it作形式賓語，when and where the meeting would be held是真實賓語。
他不清楚會議什麼時候在哪裡舉行。
5. The information on the Internet gets around much more rapidly than ____ in the newspaper.
答案A C D C D
二用適當的代詞填空
1 The quality of education in this small school is better than _____ in some larger schools.
2. An average of just 18.75 cm of rain fell last year, making ____ the driest year since California became a state in 1850.
3. To her joy, Della first earned the trust of her students and then _____ of her colleagues.
that指trust信任。
4. If you』re buying today』s paper from the stand, could you get _____ for me?
答案 1 that 2 it 3 that 4 one
1 這所小學校的教育質量要好於一些大學校的。
2 去年平均降雨量為18.75釐米，這讓去年成為自1850年加利福尼亞成為一個州以來最乾燥的一年。
3令Della高興的是，她先贏得了學生的信任，然後贏得了同事的信任。
4如果你要到報攤買今天的報紙，能不能幫我買一