an undercover agent的用法和樣例：
例句
- Sarah's first assignment as a secret agent was to protect an important witness.
莎拉作秘密特工的第一個(gè)任務(wù)是保護一個(gè)重要證人。 - It has also promised a massive security presence at the games, which may include undercover agents dressed as volunteers.
政府還承諾奧運期間會(huì )有大規?，F場(chǎng)保安人員，其中可能包括喬裝為志愿者的秘密特工。
