A30053. 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)