For years we have believed we were either healthy or sick.【51】, during the mid-1990s, scie

ntists developed a new concept called "sub-health", a status【52】health and illness. The concept of sub-health has become【53】because it has helped to explain many health problems.【54】one study, only 5. 6% of people in the overall population are actually sick,【55】the sub-healthy group consists of about 60%, and the【56】population is considered healthy.【57】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【58】turning from health to illness or from illness to health. Our bodies are actively【59】the conditions of health, sub-health and disease. Factors【60】aging, internal or external toxicity (毒性), and body or mind exhaustion may cause sub-heath, but taking good care of the body can change a sub-healthy status to a healthy one.

(51)

A．Besides

B．However

C．Meantime

D．Therefore