Frank often wears a mask _____ he can keep fit in the foggy and hazy (霾) weather.

It’s no use _______ to persuade him. You’ll only waste your time. [ ]

―I am told your class has 3 newcomers.―Yes. One is a ,the other two are .

.If you don’t know how to use an English word, the easiest way is to _____ a dictionary.

Do you mind me_______ in the dining hall-Sorry. It’s not_______.