以下函数形式中，正确的是( )
A、int func(int x,int y){     z=x+y;     return z;}
B、func(int x,y){     int z;     z=x+y;     return z;}
C、func(x,y){     int x,y;     int z;     z=x+y;     return z;}
D、int func(int x,int y){     int z;     z=x+y;     return z;}