8255只有三个普通I/O端口，所以它不可作为一个外部中断源去向8086申请中断。
参考答案：错
In our class there are 46 students, _____ half wear glasses. [ ]
A. in whom
B. in them
C. of whom
D. of them
导轨磨削方式分哪两大类各有何特点
