used to do的用法总结

　　The soldiers all used to do a six-month tour of duty in Northern Ireland.

　　士兵过去都要在北爱尔兰服役六个月。

　　I used to do that when you were a little girl, remember?

　　在你还是小女孩的时候我曾经那么做过，记得吗？

　　Potential energy can be used to do work.

　　势能可以用来做功。

　　The lecturer used to do well, but he seems to have gone off now.

　　这个讲师以前挺好，但如今似乎讲得差了。

　　I used to do it all the time.

　　我以前都是这样的。