单选题
If such unhappy persons don't change their bad behavior, the author's solution to the problem is that ______.
【正确答案】
A
【答案解析】[精解] 全文最后一句话：It will be good for others to avoid any contact with them． [B]、[C]、[D]与if they don't change这一信息无关。上文只是谈到，悲观情绪的人可能引起的反应。