单选题 下列程序中划线处正确的语句是( )。#include ＜iostream＞using namespace std;class Base{public:void fun() { cout＜＜"Base:: fun"＜＜end1; }};class Derived: public Base{ void fun() { _______________________ //显试调用基类的函数 fun() cout ＜＜"Derived:: fun"＜＜end1;};