下列程序的运行结果是 【15】 。 #include<iostream, h> class Sample { int a; public: Sample(int aa=0) {a=aa;} ~Sample() {cout<<"Sample="<<a<<;} class Derived: public Sample { int b; public:Derived(int aa=0, int bb=0): Sample(aa) {b=bb;}~De rived() {cout <<"Derived="<<b<<’’;} void main() { Derived dl (9) }