设有以下定义和程序：
#include ＜iostream.h＞
class A1

public:
void show1()

cout＜＜"class A1"＜＜endl;

；
class A2:public A1

public:
void show2()

cout＜＜"class A2"＜＜endl;

；
class A3:protected A2

public:
void show3()

cout＜＜"class A1"＜＜endl;

；
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();