设有以下定义和程序: #include <iostream.h> class A1 { public: void showl() { cout<< class A1 <<end1; } }; Class A2 : public A1 { public: void show2() { cout<< Class A2 <<end1; } }; Class A3 : protected A2 { public: void show3() { cout<<”Class A土”<<end1; } }; void main() { A1 obj1; A2 obj2; A3 obj3; } 则以下不合语法的调用语句是( )。
A.obj1.show1();
B.obj2.show1();
C.obj3.show1();
D.obj2.show2();