_____ of the students who took part in the military training is 450.
| A．A number | B．A lot | C．Lots | D．The number |
No matter ______ the CRH accident in Wenzhou, it had and will have much warning significance.
| A．how the investigators said caused | B．what the investigators said caused |
| C．why the investigators said caused | D．the investigators said how caused |
It has been announced that all the students ____ put on masks before going to school in case they are infected with SARS virus.
| A．shall | B．will | C．need | D．may |
—Have you been to the Great Wall?
—Perhaps not in my memory. ________, it might have been during my early childhood.
| A．If any | B．If so | C．If ever | D．If not |
The question that puzzled them is ____ they can get rid of the air pollution in the area.
| A．how is it that | B．that how | C．what is it | D．how it is that |
Teachers have to constantly update their knowledge in order to maintain their professional _____.
| A．consequence | B．independence | C．competence | D．intelligence |