我们需要有人帮忙打扫，而这正是你发挥作用的地方。

We need people to help clean up, and that's where you ___come ___in.

另一项措施是鼓励人们进行某种形式的锻炼，而这正是医护人员可以介入的地方。

Another measure is to encourage people to do some forms of exercise and this is where health care practitioners ___come ___in.

我们有了基础代码，但用户界面还需要完善——这就是设计师需要参与进来的环节。

We have the basic code, but the user interface needs work - that's where the designers ___come ___in.