单项选择题

有以下程序
#include ＜stdlib.h＞
gtruet NODE
int num; struct NODE *next; ;
main()
struct NODE *p,*q,*r;
p=(struct NODE*)malloc(sizeof (struct NODE));
q=(struct NODE*)malloc(sizeof (struct NODE));
r=(struct NODE*)malloc(sizeef (struct NODE));
p-＞num=10; q-＞num=20; r-＞num=30;
p-＞next=q; q-＞next-r;
printf("%d\n",p-＞num+q-＞next-＞num);
程序运行后的输出结果是

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