ationwide smog serves as a constant reminder, indicating that it’s high time we ______ on ourselves.

Tom likes playing ________ football, but his sister likes playing ________ piano.

What________ most is that Japan don’t want to say “sorry” to the Chinese people about the war.

.—- She was late for the party. —- That’s _________ she had forgotten the exact time.

Several companies are each other a contract（合同）.