40. Doctors (   ). 

• A、encourage people to take part in cold-water swimming actively
  
  

• B、point out the possible danger of blood illness during cold-water swimming
  
  

• C、believe swimming is helpful both in winter and in summer
  
  

• D、have different ideas about the medical effects of cold-water swimming
  
  

24. (   )

• A、times
  
  

• B、minutes
  
  

• C、seconds
  
  

• D、weeks
  
  

52. (    )