Please open a window _________ turning on air conditioning.
— Let’s play _____ football. —That _____ good.
A set of keys ____ in the library. Are they yours?
— Where _______your books? — _______ in the bookcase
— Does David have a ping-pong ball? —________. But he has some tennis balls.
Hi,Linda. This _____ my sister and those ______ my brothers.