Mr. Li will go to Guangzhou by air. His workmates are ______ him off at the airport.
She got __________ gifts for her birthday yesterday.
What did you buy during your last vacation? I __________ a hat.
--- ___________ there any sharks in the aquarium? --- No, we didn’t see any.
It’s not good for people __________ waste water (污水) into the river.
Every student in Miss Chen’s takes turns __________ the classroom every day.