已知L是非空单链表，head是链表的头指针，且所有结点都已具有如下形式的结构定义：
struct node
{ 
    int data;
    struct node *next;
}*p;
若要删除头结点，则下面正确的语句序列是
A、p = head;
head = p->next;
free(p);
B、head = head->next;
free(head);
C、p = head->next;
free(p);
D、head = head->next;
p = head;
free(p);