对如下代码实现的欧几里得算法(辗转相除法),执行 gcd(48, 18) 得到的调用序列为( )。
gcd(48, 18)
int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
gcd(48,18) -> gcd(18,12) -> gcd(12,6) -> gcd(6,0)
gcd(48,18) -> gcd(30,18) -> gcd(12,18)
gcd(48,18) -> gcd(18,30) -> gcd(30,6)
gcd(48,18) -> gcd(12,18) -> gcd(6,12)