Last month 3 people got injured in a gas explosion, has not been discovered yet.
| A．whose cause | B．the cause of that | C．which cause | D．the cause |
The student must be working very hard, ________?
| A．doesn’t he | B．mustn’t he | C．needn’t he | D．isn’t he |
I can’t have him _______ fun of others.
| A．make | B．making | C．made | D．to make |
At long last the child was found on top of ______ we call the museum of science and technology.
| A．which | B．that | C．what | D．where |
Personally, the job as a teacher _____ be challenging, for I sometimes _____ deal with some smarter but less diligent students.
| A．can; have to | B．may; can | C．has to; may | D．ought to; must |
Nowadays, _______ cars are more and more popular.
| A．electronic | B．electric | C．electrical | D．electricity |