下列有关预防的论述哪项是正确的（）

A.一级预防只能消除或减少机体对病因的暴露，而不具备对机体提供特异性保护的措施

B.三级预防是针对疾病自然史的不同阶段而相应地采取不同的措施

C.疾病监测属于描述性研究，而不属于疾病的预防控制工作

D.二级预防不包括临床诊断和临床治疗

E.三级预防只能提供对症治疗，而不能提供康复治疗

根据句意和首字母提示，写出所缺单词。

1. There is n___________ in the fridge. I have to buy some.

2. Before you enter the teacher's office, you must k__________ on the door first.

3. Bill Gates is a very r_________ man in the world. He has billions of dollars.

4. Mr Gao is eighty years old, but he has some m___________ ideas.

5. Can you tell me the m___________ of the word? Sorry, you should look it up in the dictionary.

6. Yang Liwei and Zhan Tianyou are national h_________.

7. Some people are p___________ flowers in the garden.