It was ___she was about to go out ___the telephone rang.
QQ, ________ you can chat with your friends, makes communication easy.
I was watching the news on TV ________ the power went off.
—How long will it be ________ the 30th Olympic Games is held in London? —It won’t be two years, I think.
When first ________ to the market, the computer software . was not a success due to its complexity in operation.
Have you ever wondered why some of the smartest students in your class sometimes ________ failing exams?