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     Signs can sometimes be seen at theentrance of a house, expressing
that a tramp has passed. This specialsign language is frequently   1   
by tramps to inform their   2   whether the host of a certain house is
friendly or unfriendly,and to  3  them the trouble of making unnecessary calls.
       Quite  4  one day, I came across a real tramp. He was such
a rare sight these days that I stood some distance away and watched
him He was dressed just as a tramp should be 5 , old worn
trousers and a jacket many sizes too big for him. On his head there
was a battered old hat and his boots were so old and worn-they
were almost coming into  6  . But the man himself looked
cheerful as if he had not a   7  in the world. He rubbed his nose
with his forefinger,   8   a funny turn, laid a small parcel by the
front gate, and began   9  a sign made by a former caller.
Although the sign was meaningless to me, it must have been  10  ,
for the tramp's face lit up with  11  . He entered the front gate
confidently and rang the bell. When the door opened, I saw him
12  his hat but couldn't hear his words. The 13 was very
short indeed, for no sooner had he spoken a few words than the door
closed fiercely in his face. I felt   14   for him as he walked  15 
out of the house. But just as quickly, his face lit up again and he
moved quickly towards the gate. There he stopped, looked at the
sign, and 16  his head seriously as if he had made a bad mistake.
 17  deeply into his pockets, he produced a piece of chalk, rubbed
out the 18 sign and made a new one in its place. He stared at it
for a moment smiling to himself, then gathered his 19 ,pushed
back his hat and began walking towards the next house at an
unhurried 20 whistling as he went along.
( )1. A. employed    
( )2. A. parents      
( )3. A. share        
( )4. A. in a way    
( )5. A. with        
( )6. A. a fashion    
( )7. A. success      
( )8. A. gave        
( )9. A. drawing      
( )10. A. pleased    
( )11. A. surprise    
( )12. A. rise        
( )13. A. conversation
( )14. A. happy      
( )15. A. cheerful    
( )16. A. waved      
( )17. A. Digging    
( )18. A. existed    
( )19. A. belongings  
( )20. A. step        		B. made          
B. classmates    
B. save          
B. by mistake    
B. in            
B. a design      
B. care          
B. took          
B. kissing      
B. strange      
B. satisfaction  
B. put on        
B. introduction  
B. frightened    
B. sadly        
B. swung        
B. Stealing      
B. moving        
B. clothes      
B. position      		C. taken      
C. fellows    
C. give        
C. by the way  
C. by          
C. pieces      
C. failure    
C. set        
C. correcting  
C. funny      
C. worry      
C. raise      
C. quarrel    
C. worried    
C. bravely    
C. shook      
C. Putting    
C. shining    
C. umbrella    
C. pace        		D. put up        
D. friends        
D. put            
D. by chance      
D. on            
D. blocks        
D. family        
D. made          
D. studying      
D. exciting      
D. disappointment
D. throw          
D. greeting      
D. sorry          
D. eagerly        
D. nodded        
D. Looking        
D. existing      
D. stick          
D. situation      
答案

1-5: ACBDB  6-10: CCDDD 11-15: BCADB 16-20: CADAC

单项选择题

某地开展某疫苗预防接种，本地7000居民中2000人接种，累计接种后两年的发病资料，7000居民中共发生本病220人，其中200名发生在未接种者中，20例发生在接种者中，发病率分别为4％和1％，两组某病发率明显差别，疫苗效果明显。此结论（）。

A.不正确，疫苗没有产生较高的免疫效价

B.不正确，未进行显著性检验

C.不正确，接种组和未接种组不是随机抽样的样本

D.正确

E.不正确，两组人数不等
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问答题

There’s a human liver sitting in a lab dish in Madison, Wis. Also a heart, a brain and every bone in the human body even though the contents of the dish are a few cells too small to be seen without a microscope. But these are stem cells, the most immature human cells ever discovered, taken from embryos before they had decided upon their career path in the body. (46) If scientists could only figure out how to give them just the right kick in just the right direction, each could become a liver, a heart, a brain or a bone. (47) When a team from the University of Wisconsin announced their discovery, doctors around the world looked forward to a new era of medicine one without organ-donor shortages or the tissues-rejection problems that bedevil transplant patients today.

Doctors also saw obstacles, though. One of them was a U. S. Congress skittish about research on stem cells taken from unwanted human embryos and aborted fetuses. Indeed, 70 lawmakers asked in a firmly worded letter that the Federal Government ban all such work.

Yet the era of "grow your own" organs is already upon us, as researchers have sidestepped the stem cell controversy by making clever use of ordinary cells. Today a machinist in Massachusetts is using his own cells to grow a new thumb after he lost part of his chest wall in an accident. A teenager born without half of his chest wall is growing a new cage of bone and cartilage within his chest cavity. Scientists announced that bladders, grown from bladder cells in a lab, have been implanted in dogs and are working. Meanwhile, patches of skin, the first "tissue-engineered" organ to be approved by the U. S. Food and Drug Administration, are healing sores and skin ulcers on hundreds of patients across the U. S.

How have scientists managed to do all this without those protean stem cells Part of the answer is smart engineering. (48) Using materials such as polymers with pores no wider than a toothbrush bristle, researchers have learned to sculpt scaffolds in shapes into which cells can settle. The other part of the answer is just plain cell biology. (49) Scientists have discovered that they don’t have to teach old cells new tricks; given the right framework and the right nutrients, cells will organize themselves into real tissues as the scaffolds dissolve. "I’m a great believer in the cells. They’re not just lying there, looking stupidly at each other," says Francois Auger, an infectious disease specialist and builder of artificial blood vessels at Laval University in Quebec City. "They will do the work for you if you treat them right."

Replacement hearts—or even replacement heart parts—are at least a decade off, estimates Kiki Hellman, who monitors tissue-engineering efforts for the FDA. "Any problem that requires lots of cell types ’talking’ to one another is really hard," she notes. Bone and cartilage efforts are much closer to fruition, and could be ready for human trials within two years. (50) And what of those magical stem cells that can grow into any organ you happen to need—if the law and biologists’ knowledge permit "Using them," says Sefton, "is really the Holy Grail.

(48) Using materials such as polymers with pores no wider than a toothbrush bristle, researchers have learned to sculpt scaffolds in shapes into which cells can settle.
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