1. The plainclothesman followed the suspect discreetly through the crowded market. (平民便装警察在拥挤的市场里悄悄跟踪嫌疑人。)

2. The plainclothesman was able to blend in with the crowd and gather valuable information about the criminal activity in the area. (便装警察能够与人群融为一体，并收集到关于该地区犯罪活动的宝贵信息。)

3. The plainclothesman was skilled at observing his surroundings without drawing attention to himself. (便装警察擅长观察周围环境，而不引起注意。)

4. The plainclothesman was able to apprehend the thief without alerting him to his presence. (便装警察成功逮捕了小偷，而不引起他的警觉。)

5. The plainclothesman worked undercover to gather evidence against the gang members. (便装警察秘密行动，收集对帮派成员的证据。)

6. The plainclothesman was commended for his bravery and quick thinking in apprehending the armed robber. (便装警察因在逮捕持枪强盗时表现出的勇敢和机智而受到表彰。)