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问题 单项选择题

以巨大岩石而成为攀岩圣地的美国国家公园是（）

A.优胜美地

B.拱门

C.死亡谷

答案

参考答案：A

完形填空
完形填空。
     Mr. Green heard that a certain government department (政府部门) wanted a clerk (职员),    1    he
wrote and    2    the position (职位). But while he was waiting for    3   , a friend of his introduced him
to the head of the department. And the head at once gave him     4   .
     Several months    5    ,    6     Mr. Green was working in the department, he got a letter from his old
address. This letter said:
"Dear Sir,
      We are    7    to have to tell you that we cannot offer you the work in this department because we do
not think that you would    8   do the job successfully."
     Mr. Green laughed, but when he looked at the letter more     9    he was     10    to see that he signed it
himself!

(     )1. A. but      
(     )2. A. got ready for
(     )3. A. an answer  
(     )4. A. the pay   
( )5. A. later    
( )6. A. so       
( )7. A. happy    
(     )8. A. have to   
(     )9. A. quietly    
( )10. A. worried   

B. so           
B. looked for     
B. his friend    
B. the address     
B. ago        
B. then        
B. sorry           
B. love to       
B. politely      
B. lucky     		C. or        
C. took      
C. the position   
C. the work  
C. before     
C. while      
C. sure    
C. be glad to    
C. carefully   
C. sad       		D. and               
D asked for          
D. the head           
D. a letter          
D. since           
D. after              
D. pleased           
D. be able to      
D. quickly       
D. surprised    
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解答题

已知函数f（x）=ex-ax，其中a＞0．

（1）若对一切x∈R，f（x）≥1恒成立，求a的取值集合；

（2）在函数f（x）的图象上取定点A（x1，f（x1）），B（x2，f（x2））（x1＜x2），记直线AB的斜率为K，证明：存在x0∈（x1，x2），使f′（x0）=K恒成立．
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