—What’s the matter with you? You look so worried.-- I don’t know ___________ the problem.
– Tom wants to know if you _________ a picnic next Sunday. -- Yes. But if it ________, we’ll visit the museum instead.
It’s a rule in my class that our classroom ______ before 6:00 p.m. every day.
Hurry up, Mike. You must get to the airport an hour before the plane _____.
-- ________ will you come back from the library, Linda? -- In an hour.
I _____ the newspaper while my mother _____ TV plays yesterday evening.