下列程序的输出结果是非曲直 【15】 。 #include＜iostream, h＞ class base int x, y; public: base(int i, int j)x=i; y=j; virtual int add()return x+ y; ; class three: public base int z; public: three(int i, int j, int k) :base(i, j)z=k; int add() return (base:: add()+z); ; void main() three * q=new three(lO,20,30); cout＜＜q-＞add()＜＜end1;