N20的中枢系统作用，正确的是（） A.吸入30%～50%有镇痛作用 B.吸入>30

根据短文内容，选择最佳答案。

     One day an Indian went to his doctor. The doctor looked him over and said, "Medicine (药)won't help

 you. You must have a good rest. Go to a quiet place for a month, go to bed early, drink milk, walk a lot,

  and smoke (吸) only one cigar (烟) a day. "

     A month later the Indian came to see the doctor again.  "How are you?"said the doctor, "I'm glad to see

  you again. You look much younger. " "Oh, doctor,I feel quite well now!"said the Indian.  "I had a good

 rest. I went to bed early,I drank a lot of milk. I walked a lot . You certainly helped me. But you told me

 to smoke one cigar a day,and that one cigar a day almost killed (杀死) me at first. It was no joke to begin

 smoking at my age. "

1. One day an Indian ______. 

    A. wasn't feeling well    

    B. went to see a friend    

    C. felt very tired  

    D. went to his doctor and helped him

2. His doctor ______. 

    A. could not help him  

    B. was good to him    

    C. told him what to do  

    D.  was glad to see him 

3. When the Indian came to see the doctor again ______. 

    A. the Indian was younger    

    B. the doctor was not free   

    C. the Indian  felt quite well   

    D. the doctor looked him over

4. The Indian told the doctor______. 

    A. he liked doing all those things    

    B. he almost killed him    

    C. to smoke one cigar a day  

    D. one cigar a day was very difficult at the beginning

5. From this story we can guess______. 

    A. the Indian was not a young man    

    B. the doctor was very interesting    

    C. the doctor was a good one   

     D. the Indian didn't smoke at first

已知等腰三角形的一边等于3，一边等于7，那么它的周长等于[ ]

A.13

B.13或17

C.17

D.14或17

如发现有计算机感染病毒，可以不将该台计算机从网上撤下，杀毒后继续使用。

工业废水中的有机污染指有机化合物引起的环境污染，下列不属于天然的有机化合物的是（）。

A.黄曲霉素

B.油脂

C.洗涤剂

D.蛋白质

如图所示，质量为48kg的小华同学骑着一辆自行车在平直公路上匀速运动500m，所用时间为100s．假设自行车在行驶过程中受到的阻力为其体重的1/12．求：在这段过程中，该同学所做的功率（取g=10N/kg）