Sally has been swimming ______four hours.

Those who have ________ floods and sandstorms know the importance of environmental protection.

Must I turn off the gas after cooking?— Of course You can never be ______ careful with that[ ]

hool isn’t the one I really wanted to go to, butI suppose I’ll just have to________ it

The movie originally ________ for children under 12 isnow being used to educate adults