Whoever leaves the room last must make sure________all the windows are shut.[ ]

Is that man Mr. Zhang—- It ______ be him. He has gone to Beijing for the meeting.

There is a new problem involvedin the popularity of private cars __________ road conditions require __________

Why is online shopping getting more popular —I think it _________ save a lot of time.

What a beautiful dress you are wearing! It must be expensive. —No. It only ____ me fifty yuan.