---Must I work out the problem right now?---Yes, you _______. It’s very serious. 

Nowadays, a graduate with a master’s degree_____ fail to find a high--paid job , which discourages a lot of college students.

(2010·辽宁高考)Doctors say that exercise is important for health, but it ________ be regular exercise.

--Morn, must I clean my room now? --No, you          . You can do it tomorrow.

_Can you write a letter in English? _No, I______.I know only a little English.