Ⅰ.单项选择
( )1.[2017·甘孜]Work hard, ________ you may catch up with your classmates soon.
A．and B．or C．but
( )2.[2017·包头改编] Find ways to praise the beginners, ________ they will lose heart someday.
A．till B．and C．or
( )3.[2017·镇江改编]—You look tired. What's wrong with you?
—I stayed up late last night. I ________ my speech from eight o'clock to midnight.
