下面程序的输出结果为:Base:: fun,请将程序补充完整。 include <iostream.h> class Base{ public: 【 】 fun(){cout<<'Base::fun'<<end1:} class Derived : public Base{ public: 【 】 fun(){ cout<<'Derived::fun'<<end1; } }; int main() { Base a,*pb; Derived b; pb = &b; pb->fun(); return 0; }