______you smile at others, they will smile back.
句意：如果你对别人微笑，他们也会报以微笑。
考查从属连词辨析。If如果；So因此、所以；Or或者；Though虽然、尽管。根据“you smile at others”及“they will smile back”可知，如果你对别人微笑，他们也会报以微笑，用If引导条件状语从句，故选A。
______you smile at others, they will smile back.
—Michael, shall we go hiking in the mountains next Sunday?
—OK, ________it rains heavily.
The young men all shouted “Happy New Year” _______it was twelve o’clock.
You’d better tidy up your room ________ your father comes back.
A break between classes is very important for students because it ________helps with students' health by doing sports _______improves their social skills by communicating with their classmates.
You'd better make a good plan you take a holiday.
Cooking is an interesting lesson and we can make different dishes ________ we like.
—Would you like to play table tennis with me this afternoon?
—I'd like to. ________ I'm afraid I have no time.
Susan ________Tina are good friends.
Miss Zhao is very helpful. She often helps us ____we are in trouble.
