it与that在句子中的用法区别

题目

it与that在句子中的用法区别
有个句子是the weather in Beijing is colder than that in Chengdu,句子中间用的是that,然后还有个句子是he found it difficult to study well ,句子中间用的是it而不是that,这是为什么?

答案

the weather in Beijing is colder than that in Chengdu,其中的that是代the weather.而he found it difficult to study well 中的it是形式宾语,是一种固定用法.此外,it还可以作形式主语,如：It is difficult for hi...