问题 完形填空
完形填空。
     Nowadays we call see more and more electric bikes in the street. Electric bikes are easy to  1  and they
can run faster than ordinary bikes. So they become very  2   in many cities in China now.
     But the electric bikes also  3  many traffic accidents happen. So the Chinese government plans to make a
new  4  for the electric bike riders (骑车者). If  5  electric bike is heavier than 40 kilos and it can go  6  than
20 kilometers an hour, its rider must get a license (执照). It means riders have to pass driving test  7  they
ride their electric bikes on the road.
     People have different ideas about the rule. Some people like the rule  8  they think it will make the street
much safer. But some people are not  9  the new rule at all. One rider said, "I don't want to get a license or
 10 ,  I don't like too many rules in life." What's your idea, my friends?
( )1. A. listen    
( )2. A. popular   
( )3. A. share     
( )4. A. message   
( )5. A. a         
( )6. A. faster    
( )7. A. during    
( )8. A. so        
( )9. A. happy with
( )10. A. something
B. ride         
B. hard         
B. throw        
B. advice       
B. an           
B. fast         
B. after        
B. because      
B. worried about
B. nothing      
C. play       
C. difficult  
C. protect    
C. rule       
C. the        
C. fastest    
C. before     
C. but        
C. sorry about
C. everything 
D. bring      
D. dangerous  
D. make       
D. letter     
D. /          
D. slowly     
D. in         
D. and        
D. surprised at
D. anything   
答案

1-5     BADCB       6-10     ACBAD

实验题

在一封闭饲养的有毛小鼠繁殖种群中,偶然发现一对有毛小鼠生产的一窝鼠仔中有几只无毛小鼠,无毛小鼠全身裸露无毛,并终身保留无毛状态。科研人员为了研究无毛小鼠的遗传特性,让上述这对有毛小鼠继续杂交,仍有无毛鼠出生;让无毛小鼠与亲代有毛小鼠回交,生产出10只无毛小鼠和12只有毛小鼠,其中无毛小鼠雌雄各5只,有毛雌小鼠7只,雄小鼠5只。

(1)科研人员初步判断:

①.该小鼠无毛的原因是种群中基因突变造成的,而不是营养不良或其他环境因素造成的;

②.控制无毛性状的基因位于常染色体上。

科研人员对第①项判断作了解释:因为小鼠无毛的性状可遗传给后代,是可遗传的变异,种群中常见种为有毛,出现无毛性状最可能是基因突变的结果。

请你写出对第②项判断的理由:_________________________。

(2)由于该种无毛小鼠有极大的科研价值,科研人员需要将其扩大繁殖。已知无毛是由隐性基因控制,无毛雄鼠能正常生育,无毛雌鼠繁殖力低,哺乳困难。若利用上述回交实验得到的小鼠做实验材料,理论上有四套交配方案能获得无毛小鼠。

其方案一为:杂合有毛小鼠♀×杂合有毛小鼠♂

写出另三套方案,指出最佳方案并说明理由。

方案二:_________________________________ 。

方案三:_________________________________ 。

方案四:_________________________________。

最佳方案:_________________________________。

最佳方案的优点:________________________________________________。

其余方案的缺点:______________________________________。

单项选择题