while前后连接的时态是不是一样的

　　It will take a while for the drug to work out of your system.

　　这药得需要一段时间才能排出你的体外。

　　I'll be back in a little while.

　　我一会儿就回来。

　　You'll water the plants while I'm away, won't you?

　　我外出的时候请你给花草浇浇水，行不行？

　　Her parents died while she was still at school.

　　她还在读书时父母就去世了。

　　He'll do the job if you make it worth his while.

　　你要是给他的报酬丰厚，他会做这份工作的。