我国标准规定，在缩分过程中，每一阶段的留样量取决于（）。
A.煤样量
B.煤样粒度
C.视具体情况而定
D.制样人员多少
参考答案：B
胸外按压放松时掌根不得离开（）。
A.胸骨
B.四肢
C.胸壁
D.胸前
The major goal of USB was to define an external expansion bus which makes adding (70) to a PC as easy as hooking up a telephone to a wall-jack. USB 2.0 is an evolution of the USB 1.1 (71) , providing a higher performance interface.
A．peripherals
B．outside
C．inside
D．beside
