H-4：have a card up one's sleeve 心中有数
A:Do you think Tom can remain at the top of the class this time?
A:你认为汤姆这次还能保特全班第一吗？
B:I believe so. He seems to have a card up his sleeve.
B:我相信他能。他看起来胸有成竹。
A:All his confidence comes from hardworking.
A:他的自信源于他的勤奋。
B:Yeah. he's the most diligent student I have ever met.
B：是啊，他是我见过的最勤奋的学生了。
