Had I been a little more careful,I________such a foolish mistake.  [ ]

A. won't make  

B. hadn't made

C. didn't make  

D. wouldn't have made

计算机病毒可以使整个计算机瘫痪，危害极大。计算机病毒是

A．一种芯片

B．一段特制的程序

C．一种生物病毒

D．一条命令