_________ call your best friend up – That’s a good idea.

The organizers promise________wins the first prize a chance to go abroad。

Kunming is a beautiful city ________ flowers and green grass and trees are seen all year round.

The salespeople said they hadn’t overcharged customers, but the police’s report showed that the practice did ______

What does PM2.5 mean— It’s a professional ______ indicating the condition of air pollution.