Maybe I won’t come back _____ six o’clock. So don’t wait. [ ]

Excuse me. You shouldn’t smoke here. Look at the sign “NO SMOKING HERE”.–Sorry, I ________ it just now.

More than 20 people ________ in traffic accidents ________ last May.

____ troubles me most right now is____ I can’t remember where I have put my car keys.

___ _? —It’s hard to say. If there were no examinations, I should have a much happier time at school.