如果1个钻机每0.15秒钻1个孔，那么，该钻机1小时能钻多少个孔()
A．2400B．5400C．24000D．5400O
参考答案：C
Jim is a ____ boy, and today is his _____ birthday.
A．twelve-years-old, twelve
B．twelve-years-old, twelfth
C．twelve-year-old, twelve
D．twelve-year-old, twelfth
20，112，512，952，( )
A．7778 B．7779 C．7789 D．8978
