根据语篇情景，用恰当的短语或句子填空，使之意思完整。

     If you often feel tired, and the doctor can’t find anything wrong with you, you may be in a state of sub-health（亚健康）. Sub-health is a state between health and illness. Most of the sub-healthy people are middle-aged ones who 1.____________ because of work and family. And some of them are students who are having exams.

     If you are sub-healthy, it’s not difficult for you to recover（恢复）. You should 2.____________. For example, you should get up early and go to bed early. And you should exercise regularly. Exercising can keep you healthy. As for meals, it’s better to eat less salt and sugar. Vegetables, fruit and fish are important to your body. You should eat more of them. It’s not good to eat too much at one meal, because it is bad for your digestive tract（消化道）. In a word, 3.____________ is very helpful in avoiding（避免）sub-health.

以行为科学为理论依据，作为行为科学的一部分存在的理论是( )。

A．古典组织理论

B．近代组织理论

C．现代组织理论

D．组织行为理论