有如下程序: #include<iostream> using namespace std class Base { public: void fun() { cout<<'Base::fun'<<endl } } class Derived: public Base { public: void tim() } ____________ cout<<'Derived:: fun'<<endl } } int main() { Derived d d.fun() return O } 已知其执行后的输出结果为: Base::fun Derived::fun 则下划线处应填入的语句是