---Who is that woman? ---She is ________ mother.
By looking at a problem in as many ways as possible, creative thinkers can find solutions that would _______ remain invisible.
—What has made him upset recently? —_______ alone to face a troublesome milk case.
—What are you doing, John? Why stop?—To be on the safe side, we’d fill up the car now for we _______ run out of gas on the way.
When he realized the police had spotted him, the man _______the exit as quickly as possible.
Bill Gates has created a wonderful “window” ______ people can surf the Internet freely.