按规定高压验电器每年必须进行（）次检验。
A、一
B、两
C、三
D、四
参考答案：B
—How long have you _____ the bike.
—For about two weeks.[ ]
A. bought
B. buy
C. buyed
D. had
The weather in this area is generally warm，but it be very cold sometimes．
A．must
B．can
C．should
D．need
weather in this area is generally warm，but it be very cold sometimes．