You __________ buy a gift, but you can if you want to.
| A．must | B．mustn’t | C．have to | D．don’t have to |
—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 |
“I don’t think it’s my _______ that the TV blew up. I just turned it on. That’s all.” said the boy.
| A．error | B．mistake | C．fault | D．duty |
—Look! Somebody _____ the sofa.
—Well, it wasn’t me. I didn’t do it.
| A．is cleaning | B．was cleaning |
| C．has cleaned | D．had cleaned |