If you are free to walk through out city, please ________ us.A drop in B drop in at C. drop in on
The Smiths came to Shanghai in 2008,they ____ there for three years since then.
It’s raining heavily outside. Why don’t you _______ your raincoat?
Last year, I visited a chemical factory in Baise, there are about _____ workers in it.
Many people have got the habit of buying flowers for their mothers on _______.
I found a story-book on the desk, it isn’t mine, it is ___,I think.