--- Jack lost new mobile phone the other day.
--- ________? That’s his third one in just one month.
A. Had he B. Did he C. Does he D. Has he
It remains ________ whether he will be experienced enough to take over the business.
A. seen B. to be seen C. seeing D. to see
When first to the market, these products enjoyed great success.
A. introducing B. introduced C. to introduce D. being introduced
So sudden ______ that the workers left behind had no time to escape.
A. did the outbreak of the fire B. the outbreak of the fire did
C. was the outbreak of the fire D. the outbreak of the fire was
______ the Internet is of great help, I don’t think it’s a good idea to spend too much time on it.
A. If B. As C. Because D. While
Gun control is a subject ______ Americans have argued for a long time.
A. of which B. with which C. over which D. into which
