为什么the weather in shanghai is better than that in england.the weather in shanghai is better than that in england.句中用thatthis car is quite different from_______i bought last year 句中用the one,有什么区别

这只能说是习惯吧.

在比较级的句子中，一般只用that或those来代前面的成分，如第一句中， that 就是代the weather 的。
而第二句中，“_______”中的既要做主句的宾语，又要做“_______last year”中的先行词（相当于 i bought sth. last year ）所以要用the one

the weather in shanghai is better than that in england.句中的that是代词，是泛指，指the weather.
this car is quite different from the one i bought last year 句中用the one是特指，虽然还是指代car，但是有后置定语加以限制，特指"我去年购买的轿车"，区别于this car.

因为汽车是一个东西，所以说 "the one"， 而天气算是一个概念，只能用"that".

句中的that是指代前面的the weather 的,相当于the weather in shanghai is better than the weather in england.很显然这里用the one 是不合适的.
后面句子中的the one 指的是car 这个物.