phr. Is it cheaper to travel by train instead of by air?
phr. Are we going to take the elevator and go upstairs now?
phr. Is it because of the cold weather now that people in Beijing eat hotpot a lot ?
phr. Is this a photo of your family?
phr. The speed of my computer has become slower and slower. Could it because it has viruses?
phr. Dad is very busy, isn't he?