下面程序执行后的输出结果是()。#include #include struct NODE { int num; struct NODE *next;};int main(){ struct NODE *p, *q, *r; p = (struct NODE *) malloc( sizeof(struct NODE) ); q = (struct NODE *) malloc( sizeof(struct NODE) ); r = (struct NODE *) malloc( sizeof(struct NODE) ); p->num = 10; q->num = 20; r->num = 30; p->next = q; q->next = r; printf( "%d", p->num + q->next->num ); return(0);}

A. 10
B. 20
C. 30
D. 40