If you are free to walk through out city, please ________ us.A drop in B drop in at C. drop in on
_______ good suggestion ! I haven’t heard of _______ wonderful advice for a long time.
__________ good advice the teacher gave me!
_______________ useful message he got from his mobile phone this morning!
----______ nice present you've bought for me!----I'm glad you like it.
________ tall the girl is!