around(围绕)

　　We all drew up closely around him.

　　The guide showed us around the city.

　　(show sb. around 领某人参观)

　　at(在……)

　　Let’s meet at the station.

　　She was at a conference.

　　The committee is to meet at the weekend.

　　He joined up at eighteen.(join up 参军)

　　What are you laughing at? (laugh at 嘲笑)

　　Let’s have a look at the picture. (have a look at 看一看)

　　My mother was surprised at the news.(be surprised at 吃惊)

　　He is good at mathematics.(be good at 擅长)

　　He is good at drawing.