二、 one
可以代替與前面同類不同一的事物；可以代替某類事物中的任何一個；可以做同位語，重復指代前面的事物，其后有定語從句用以進一步說明前面的名詞。
one表泛指，相當于a/an+名詞。
one只能代替可數(shù)名詞，其復數(shù)形式是ones。
one可以根據(jù)語義在它的前面或后面加上一些定語。
one前面不能直接加不定冠詞（a / an）或物主代詞，one前已經(jīng)有形容詞時，則可以加不定冠詞或物主代詞；one前加the與否，取決于是否特指，如果特指就加the。
one既可以代指物，也可以代指人。
三、 that
代替與前面同類不同一的事物。
that表特指，相當于the+名詞。
它可以代替可數(shù)名詞，也可以代替不可數(shù)名詞。代替可數(shù)名詞時，復數(shù)形式為those。
that可以根據(jù)語義在它的后面加上一些定語，多數(shù)是of短語；它的前面不能存在任何定語。
that只能代指物。
四、例句分析：
I have lost my umbrella; I'm looking for it. （該句中it就是指前面的my umbrella）
I have lost my umbrella; I think I must buy one. （one在該句中表泛指，因為my umbrella已經(jīng)丟了）
The umbrella you bought is cheaper than that I bought. （替代詞that在該句中特指“the umbrella I bought”，以區(qū)別“the umbrella you bought”）
A chair made of steel is stronger than one made of wood. （該句中one可以換成a chair）
The water in the cup is hotter than that in the pot. （該句中that可以換成 the water）
I like this pen more than that one. （one代替可數(shù)名詞單數(shù)pen）
There were a few young people and some older ones in the house. （ones代替可數(shù)名詞復數(shù)people）
Mary's handwriting is far better than that of Peter. （that代替不可數(shù)名詞 handwriting）
These pictures are more beautiful than those. （those代替可數(shù)名詞復數(shù) pictures）
The one ／That on the table is mine. （該句中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. （該句中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. （該句中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.