be good at后加什么形式

　　雙語例句：

　　1、You have to be good at spotting trouble on the way and heading it off.

　　你必須善于發現潛在的麻煩并加以化解。

　　2、A teacher should be good at drawing inferences about other cases from one instance.

　　老師要善于舉一反三。

　　3、Viruses tend to be good at surviving when a computer system crashes.

　　計算機病毒在系統崩潰后往往依然存在。