able的名詞形式是什么?

　　They overestimated his ability when they promoted him.

　　他們提拔他的時候高估了他的能力。

　　Contestants were grouped according to age and ability.

　　參賽者按年齡和能力分組。

　　His outstanding ability earned him a place on the team.

　　他非凡的能力為他在隊中贏得了一席之地。