undercover operation 秘密行动
intelligence agent 情报人员
secret agent 特工
investigative officer 调查人员
1. The undercover agent successfully gathered all the necessary intelligence.
那名卧底特工成功搜集到了所有必要的情报。
2. He worked as an undercover agent to infiltrate the organization.
他作为一名卧底，渗透进该组织。
3. The police sent an undercover agent to monitor the suspicious activities.
警方派出一名卧底去监视这些可疑活动。
A: Did the police identify the undercover agent?
A：警方识别出那名卧底了吗？
B: No, his identity remains a secret.
B：没有，他的身份仍然是一个秘密。
1) 卧底
2) 秘密特工
3) 秘密调查人员
1. 卧底；秘密特工
e.g. An undercover agent was sent to investigate the case.
一名卧底被派去调查此案。
noun phrase
1. A person who works secretly to gather information or catch criminals.
Synonym: spy, mole