有两个句型一直不明白,关于it 和it is

问题描述:

有两个句型一直不明白,关于it 和it is
有两个句型一直不明白:
1.He found it difficult to climb the stairs.
2.He thinks that it is better to see the movie than to read the book in original.
为什么第一个是it而第二个是it is?

前者是it作形式宾语,后者是it is作宾语从句中的主语和系动词两者有区别,但也可以互换,请看:He found it difficult to climb the stairs.=【He found that it is difficult to climb the stairs.】He thinks that it...