To take one unaware

• 出其不备

To take one unaware的用法和样例：

例句

1. I tried to follow her but she gave me the slip.
   我想跟住她，她却乘我不备溜走了。
2. The girl yearned towards the secular life and her lover, then one day she escaped successfully in advantage of the guard's carelessness.
   姑娘日夜思念小伙子，终于有一天趁看守不备跑了出来。