欧几里得算法又称作辗转相除算法，下面程序中是这种算法的是（ ）
def gcd(a,b):
if b == 0:
return a
return gcd(b, a % b)
def gcd(a, b):
if a < b:
a, b = b, a
while b != 0:
a,b = b,a%b
return b
def gcd(a,b):
if b == 0:
return a
return gcd(a, a % b)
def gcd(a,b):
if b == 0:
return a
return gcd(b, b % a)