特种作业风险较高,为保证作业人员和他人的安全,特种作业人员必须持证上岗。特种作业人员操作证的复审每( )年进行一次。
A.1
B.2
C.3
D.4
参考答案:B
2464与480的最大公约数为 [ ]
A.32
B.23
C.42
D.7
She listens to the radio every day, ______? [ ]
A. doesn't she
B. isn't she
C. hasn't she
D. won't she