有如下程序: #include<iostream> using namespace std; class Base { private: void funl()const {cout<<"funl";} protected: void fun2() const{cout<<"fun2";} public; void fun3() const {cout<<"fun3";} }; class Derived:protected Base {public;void fun4() const {cout<<"fun4";} }; int main() { Derived obj; obj.funl();//① obj.fun2();//② obj.fun3();//③ obj.fun4()://④ return 0; } 其中有语法错误的语句是
A.①②③④
B.①②③
C.②③④
D.①④