一般光面滚筒摩擦系数在（）左右。
A.0.2
B.0.5
C.0.7
D.0.9
参考答案：A
––Mrs Zhang is very popular among the students.
––Yes. Her classes are ______ lively and interesting.
A．always
B．hardly
C．never
D．sometimes
— Why do you look so worried?
— I bought an MP5 player yesterday, but I can't find _____ anywhere now.[ ]
A. it
B. one
C. any
D. that
