下列计算最大公约数的递归过程，正确的是___________。
选项：

A: Sub gcd(ByVal m%, ByVal n%) Dim r% r = m \ n If r = 0 Then gcd = n Else gcd = gcd(n, r) End If End Sub ;
B: Sub gcd(ByVal m%, ByVal n%) Dim r% r = m Mod n If r = 0 Then gcd = n Else gcd = gcd(n, r) End If End Sub;
C: Function gcd%(ByVal m%, ByVal n%) Dim r% r = m \ n If r = 0 Then gcd = n Else gcd = gcd(n, r) End If End Function;
D: Function gcd%(ByVal m%, ByVal n%) Dim r% r = m Mod n If r = 0 Then gcd = n Else gcd = gcd(n, r) End If End Function