1. My brother John is an expert in video games.2. I am a pro in billiards because I have been shooting pool for ten years now.3. I have to admit I'm not a pro at computers. I often need to ask my son to fix my computer for me.
 an expert in something a pro in something a pro at something白話的翻出即可.
Many people break traffic laws. Police officers cite traffic offendrs.