it is a long story说来话长；一言难尽
It is a pity that 遗憾的是
it is asserted that有人断言；有人主张
it is assumed that假定；人们认为；据推测
it is certain that毫无疑问……；肯定……
It is considered that据知
it is important这非常重要 it is important for sb to do：对某人来说做某事重要
It is important that ...：重要的是
It is learned that据悉…；众所周知
It is no use doing：做.是没用的
it is obvious that显然…
It is raining下雨了
it is reported that据报道
It is said that：据说；有人说,；据说……
It is suggested that ...：建议,有人建议
It is supposed that...：据推测,人们猜测
it is the same with亦复如是
it is time to do sth.：是时候做什么事情了；是该做某事的时候了
it is time for sb to do：该是做某事的时候了