—Who’s that boy reading in the study ? Is it David?—It __________ be David. I saw him go home just now.
Call a taxi, ______ you will miss the train.
Don’t make ________in class.
_______ you do, don’t miss this exhibition, for it’s so hard for me to get the tickets.
You shouldn’t watch TV____ school nights.
--- I can’t fall asleep. --- You get up and try to do something ______lying in bed.