4-f
n. [美国英语]；选征兵役制中不及格者免除兵役(者)(指身体、心理、品德等不适于服兵役)的分类
🗣️ 情景例句
You must be mistaken.
你一定搞错了。
Don't forget to print airmail on the letter.
不要忘记在信封上印上航空邮件
I don't care for very hot weather.
我不喜欢热天。