两种情况
1、It's 是 It has 的缩写,比如
It's gone.它已经走了.
It's reported that.XXX已经被报道过了.
2、It's 做形式主语,表示客观事实.比如It's hoped大家希望都
It'sreported据报道
It's believed 大家都相信
It's said 大家都说
It's known 众所周知