运行下列Python程序后的结果是？（ ）
def f(n):
n=n*2
return n
a=[7,1]
b=f(a)
print(a,b)
[7,1],[7,1,7,1]
[7,1],[14,2]
[7,1],[7,1],[7,1]
[7,1],[7,1]