For years we have believed we were either healthy or sick. (55) , during the mid-90s, scientists developed a new concept called "sub-health", a status (56) health and illness. The concept of sub-health has become (57) because it has helped to explain many health problems. (58) one study, only 5. 6% of people in the overall population are actually sick, (59) the subhealthy group consists of about 60%, and the (60) population is considered healthy. (61) of one’s sub-health will help one to be alert to the underlying disease and remain healthy. Sub-health is a state in which the body is (62) turning from health to illness or from illness to health. Our bodies are actively (63) the conditions of health, sub-health and disease. Factors (64) aging, internal or external toxicity (毒性), and body or mind exhaustion may cause sub-health, but taking good care of the body can change a sub-healthy status to a healthy one.
56().
A.already
B.still
C.neither
D.either
参考答案：D
解析：
本题测试固定搭配either...or...文中说亚健康是身体从健康变得不健康或不健康变的健康的一种阶段。already意为“已经”；still意为“仍然”；neither可用于固定搭配neither…nor…中，意为“既不……也不……”；either用固定搭配either…or…中，意为“或者……或者……”。D为正确答案。