：已知last指向单向简单链表的尾结点，将s所指结点加在表尾，不正确的操作是____。A:s->next=NULL, last->next=s,last=s;B:last->next=s,s->next=NULL,last=s;C:last->next=s,last=s,last->next=NULL;D:s->next=NULL, last->next=s, s=last;答案: s->next=NULL, last->next=s, s=last;5、