有如下程序: #include<iostream> Using namespace std; class Base public: Base(int x=0):valB(x)cout<<valB; ~Base()tout<<valB; Private: int valB; ; class Derived:public Base public: Derived(int x=0,int y=0):Base(x),valD(y)cout<<valD; ~Derived()cout<<valD; private: int valD; ; int main() Derived obj12(2,3); return 0;