I think _______ our duty to keep our environment clean and tidy.

I hear that Lily’s brother is a worker here.—Look! The manis working over there is her brother.

Can I look up a word ____ your dictionary? — I haven’t got ____ me. [ ]

How do you like working here?—_______.To be honest，I miss my former colleagues．

Tom, _____ students are there in your class? —_____[ ]