以下哪个定义中的p不是指针，请选择恰当的选项：

int main(void)
{
int m[ ][3] = { 1, 4, 7, 2, 5, 8, 3, 6, 9 };
int i, j, k=2;

for (i=0; i<3; i++)
printf ("%d ", m[k][i]);

return 0;
}

int main(void)
{
int aa[4][4]={ {1, 2, 3, 4}, {5, 6, 7, 8}, {3, 9, 10, 2}, {4, 2, 9, 6} };
int i, s=0;

for(i=0; i<4; i++)
s += aa[i][1];
printf("%d\n", s);

return 0;
}

int a[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, *p = a, i;

char s[ ]="china";
char *p;
p = s;

struct student{
int num;
int age;
};
struct student stu[3] = {{101, 20}, {102, 19}, {103, 20}}, *p = stu;

struct Student{
char name[10];
int age;
char gender;
}std[3], *p=std;

则以下各输入语句中错误的是：

struct  ex {
int x;
float y;
char z ;
} example;

struct student
{
int no;
char name[20];
char sex;
struct{
int year;
int month;
int day;
}birth;
};
struct student s;