焊剂按化学成分分为( )。
A．烧结焊剂
B．碱性焊剂
C．酸性焊剂
D．中性焊剂
参考答案：B,C,D
Computer systems consist of two very different types of elements: (71 ) , which includes all the physical things that can be touched and Software, which tells the hardware how to do.
A. Operating system B. I/O devicesC. Courseware D. Hardware
在“若三言三止，脉之咽唾者，此诈病也”中，“三”之义是（）
A.虚数
B.序数
C.比较数
D.乘数
