From space, the earth looks blueThis is ____about seventy-one percent of its surface is covered by water

Could you meet me at the airport—I’d like to，but I ________Shanghai when you return.

our city, smoking is not _____ insuch public places as the cinema, the theater, the library and the museum

They keys were __________ to our neighboursduring our absence.

One is never ______ old ______learn. Do you think so —Yes., I agree.