单选题
以下代码用于生成 位格雷编码。横线上应填写（ ）。
A
result += ["1" + s for s in reversed(prev)]
B
result += ["0" + s for s in reversed(prev)]
C
result += ["1" + s for s in reversed(1)]
D
result += ["1" + s for s in reversed(0)]