//静态成员函数使用 #include int sum=0; class sample { public: sample (int i,int j); static void addnumber(); private: static int a,b; }; int sample::a=0; int sample::b=0; sample::sample(int i,int j) { a=i; b=j; } void sample::addnumber() { sum+=a+b; } void main() { sample x(1,2),y(3,4); ________::addnumber(); cout<<"sum ="< <