Barack Obama has taken personal blame ____ the security failures which led ____ the attempt to

blow up a plane on Chrismas Day.[ ]

A. of; to          

B. for; to      

C. on; on            

D. in; on

为保证数据输入的正确性，通常在代码结构中加入( )。

A．十进制编码

B．校验码

C．专用编码

D．组合编码