[Modal auxiliaries] Expressing Necessity: Must, Have To, Have Got to

	degree
I must study.	Very important
I have to (need to ) study. have to (hafta) has to (hasta)	Important
I have got to(gotta) study.	Not so important

Must have 一定

They must have missed the call.

Could have 原本可以，差點就能

She could have arrived by now. 

Our team could have won.

You need not do this! Visa is a must. black book (c) 7. If you dog is running free and the police stop you, you will probably ___ pay a fine. a. must b.must not c have to d. don't have to (must 用未來式怪怪的) You have to finish your project before getting off work.