i think it not difficult to keep reading. 形式主语为什么

形式主语it 难题Do you think it difficult to work out this question 主语think it difficult to与think it's difficult to的区别 为什么有的时候是I think 有的时候是I think it is difficult to do sth 英语不太好,First of all I think it not very difficult to learn En I think it difficult to answer this question 为什么可以it 不加is? I think it difficult to learn English well句中为什么用it? i think it's easy for me to learn english.那是形式主语还是宾语 I think it bad manners to smoke in a reading room.为什么不用it's, I think geography is difficult to learn it. I found it difficult to get to sleep.主语是 to get to sleep? it形式主语从句it作形式主语It makes me sick to think about the problem那是 I think it hdrd to learn English.哪个是主语?