船长接到火警信号后应采取的行动是：

A、立即奔赴现场指挥

B、立即找大副商讨灭火方法

C、立即上驾驶台指挥

D、立即找报警人查明火情

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.

57().

A.choosing 

B.comparing 

C.improving 

D.balancing