核心问题
its与it's有无区别？
词典解答
its 是 it 的物主代词(即所有格)，而 it's = it is 或 it has。
It's no use
It's no use doing/It's no use to do 见 it
It's time + 不定式或过去时 见 It's time for us to go
It takes/took a long time to do sth. 见 take
It was not until. 见 until( It was not until)
item 见 news, piece/item