K-2：keep one's ear to the ground 全神贯注地听
A:John! John!
A:约翰！约翰！
B:Er... Yes, Madam?
B：哦……老师。
A:What are you thinking about? You are distracting again. Keep your ear to the ground.
A;你在想什么？你又走神了！注意听讲。
B:I am sorry, Madam.
B：对不起，老师。
