有以下程序：#include ＜iostream＞using namespace std;class sample{private: int x; static int y;public: sample(int a) ; static void print(sample s);};sample:: sample(int a) { x=a; y+=x;}void sample::print(sample s){ cout＜＜ x= ＜＜s. x＜＜ , y= ＜＜ y＜＜end1;}int sampte::y=0;int main(){ sample s1(10); sample s2(20); sample::print(s2); return 0;}程序运行后的输出结果是
A．x=10,y=20
B．x=20,y=30
C．x=30,y=20
D．x=30,y=30