We planted trees last year.
--- “Why don’t you go to the Science Museum?” ---“I hear there’s ______ in it.”
Our teacher is coming. Please stop _____ and keep ________.
There are many CD-ROMs in the bookshop. I don’t know ____ to buy.
---Hello, may I speak to Millie? ---Sorry, she isn’t in. She _________ Nanjing.
I_______ the piano for two years.