onlyif的用法有哪些

　　I'll do that, but only if we set a few rules.

　　我可以干，但我们得定几条规矩。

　　You can make progress only if you are modest.

　　惟虚心乃能进步。

　　The medicine works only if taken for a long time.

　　此药久服方见功。

　　I'll go only if you go with me.

　　除非你跟我去，我才去。

　　One can grasp a foreign language only if he studies hard.

　　唯有努力学习，才能掌握外语。