1. it 指代前面提到过的同一事物，即同名同物
例图：I left my key in my drawer, but today it is gone.(it 指上文提到过的key)
我把钥匙放抽屉里，可是今天不见了。
2. one 泛指与前面的名词同类的另一事物，即同名异物，其复数形式是ones
例图: I don`t like this type of computer. Could you show me a better one?(one 指computer，但不是上文提到过的)
我不喜欢这种款式的电脑，能给我拿一个更好一点的吗？
3. that 特指的名词与前面的名词只是同一类，但并非同一个，即同名异物。that可以代指可数名词单数和不可数名词，但只能指事物，不能指人。其复数形式是those，those只能代替可数名词复数，可以指人或物。
例图：The weather in Guangzhou is hotter than that in Beijing in summer.(that指the weather. 但不是同一地区的)
夏天，广州的天气比北京热。
4. one 与that 都指代同名异物，但one是泛指，相当于a/an+名词，所以one所指代的名词修饰语一般为a/an/some/any.
例如： A chair made of steel is stronger than one made of wood.
而that为特指，相当语the+名词。所以that指代的修饰语一般是 the/this/that.
例如：The water in the cup is hotter than that in pot.
5. 习题巩固
I`m moving to the country because the air there is much fresher than ___in the city.
Meeting my uncle after all these years was an unforgettable moment, ___ I will always treasure.
I like ____ in the autumn when the weather is clear and bright.
答案：1. that 2. one 3. it