从前的英文短语once

　　Once upon a time, a group of men came to a rainforest.

　　从前,一群人来到一片雨林。

　　Once upon a time, there was a tree which wanted to become a treasure box.

　　从前,有一棵树想成为宝箱。

　　If necessary I can come at once.

　　如果有必要，我可以马上来。

　　A computer can perform many tasks at once.

　　电脑能同时做多项工作。

　　Since the party she had only spoken to him once.

　　那次聚会以后，她只和他说过一次话。