My mother passed the driving-test at her first attempt. It was all ______ she had been practicing so hard.

A. why        

B. because    

C. that            

D. what

设8086系统中采用单片8259A，其8259A的ICW₂=32H，则对应IR₅的中断类型号为（）H，它的中断入口地址在中断向量表中的地址为（）H。