41. According to the passage, some doctors believe it is true that (   ). 

• A、you are healthy if cold-water swimming turns your skin color blue
  
  

• B、cold-water swimming causes more heart attacks in summer than in winter
  
  

• C、cold-water swimming can make the body temperature dangerously high
  
  

• D、Polar Bears are bears swimming in freezing water
  
  

53. (    )

13. It was buying game cards that cost Jim most of the money that he (   ) on learning. (   ) 

• A、might have spent
  
  

• B、must have spent
  
  

• C、should have spent
  
  

• D、 would have spent