Do you think th important for us to learn a foreign language

Do you think th important for us to learn a foreign language
这句话为什么是it important不是it is 那什么时候用it is important 还有一个我觉得类似 i dont think physics easy to learn 这句话成分怎么解释

Do you think it important for us to learn a foreign language?中的it是形式宾语,真正的宾语是动词不定式to learn a foreign language.
在英语中,如果动词不定式或从句做宾语,后面有宾语补足语,往往用it作形式宾语把真正的宾语放在后面.
.这句话也可以改成：Do you think（that） it is important for us to learn a foreign language?吥过,在这个句子中,it is important for us to learn a foreign language?是宾语从句.而在这个宾语从句中,it是形式主语,真正的主语是动词不定式to learn a foreign language.
I don’t think physics easy to learn这个句式与上一个有所不同.physics是宾语,easy to learn是形容词短语作宾语补足语.这种形容词短语,除了作宾语补足语外,还可以做表语.
例如：Physics isn't easy to learn
.再如：He is easy to get on well with.