it作形式主语和宾语

　　A形式主语

　　⑴It’s +adj. +for/of +sb. to do sth.

　　It’s very kind of you

　　It’s important for you to learn English well.

　　⑵It’s time for sb.to do sth.

　　It’s time for you to sing

　　⑶It seems that .....It seems that you are right.

　　⑷It’s one’s turn /job/duty to do sth.

　　It’s your turn/job/duty to clean the desk.

　　⑸It’s +adj. that 从句It’s necessary/certain/natural that he wiil win.

　　⑹It’s no use /good doing sth.做某事没有用处/好处。

　　It’s no use /good eating too much

　　⑺It’s +一段时间since +一般过去时态从句或It has been +some time +since +一般过去时态从句It’s(been) five years since we saw last .

　　⑻It’s a pity that ......It’s a pity that only six pieces of music in total were recorded for the future world to hear.

　　⑼It is said that/It is consider that/It is believed that ......It is said that he became a famous pianist.

　　B形式宾语

　　动词(feel，think，make,believe,consider,suppose等)+it +adj./n.+ to do sth.

　　I think it necessary to learn English well.