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();