以下代码的输出结果是（ ）

a = [5,7,6,3,4,1,2]
b = sorted(a)     
print(a )

A、[5,7,6,3,4,1,2]
B、[1,2,3,4,5,6,7]
C、 [7,6,5,4,3,2,1]
D、[2,1,4,3,6,7,5]