单项选择题
A.0000010B.1111101C.0010010D.1101101
A.y6有效,管脚输出为11011111B.y6有效,管脚输出为00100000C.y5有效,管脚输出为00100000D.y5有效,管脚输出为11011111
A.2nB.2nC.2n-1D.2n-1