设有以下定义和程序：
#include＜iostream.h＞
class A1
public:
void show1()
cout＜＜"class A1"＜＜end1;
;
class A2:public A1
public:
void show2()
cout＜＜"class A2"＜＜end1;
;
class A3:protected A2
public:
void show3()
cout＜＜"class A1"＜＜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();