The floor is clean and dry now. Who _______?— Sorry, I don’t know.

______ does she play volleyball every day? —_____ half an hour.[ ]

My grandma started using Weibo at the age of 70. She always says it’s never ____ old to start doing things.

Where did you get the book? —- From the library．And I have _______it for two weeks．

He said that light ______much faster than sound.