英语once 一旦.,表示时间和条件 说两个关于once的句子.

Once you understand this rule,you will have on further difficulty.
一旦伱理解了这条规律,你就不再感到困难了. 再答： Once you have decided to do something,you should do it well. 一旦伱已经决定了要干什么事情，就应该把它做好。