A. a gradual parting from the real world B. undisturbed by tension or problems C. drowning in an ocean of darkness D. dependent only Upon individual age and health 参考答案:A 答案解析:因为全文通篇在描述睡眠。文章纠正了过去的旧观念,也不认为它与测到的 myoclonic jerk有多大关系,D项所谓的个体的年龄和健康状况也未见文中有述。