keep one's ear to the ground 全神贯注地听
【讲解】
to the ground有“全部，完全，彻底”之意。让耳朵完全瞀觉起来，引申为“全神贯注地听”。
【对话】
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。