完整形式是it has，例如：
1.It has been demonstrated that this drug is effective.这药已证实是有效的。
2.It has been confirmed that the meeting will take place next week.已经确定会议将于下个星期召开。
it's完整形式: it is
It's satisfying when the results are good .
叫人满意的是，结果圆满。
It's the last-ditch fight for them .
这就是他们生死存亡的最后一搏了。
It's because you're not drinking it on the run .
这是因为你不常喝。
It's wrong to pet a big boy like you .
宠爱你这么大的孩子是错误的。
Don't thank me; it's an honest appraisal .
不必谢我，这是诚实的评估。
It's good to meet a girl who's got wit .
难得碰上一个会打趣的女子。
It's disease of the last five thousand years .
这是五千年来的病症。
