54. (   )

39. If the information given in this passage is correct, when we look at a star at night (   ). 

• A、we will notice that it is not moving
  
  

• B、we cannot tell whether or not it still exists
  
  

• C、it is four years that the light we can see will reach us
  
  

• D、it will be brighter than the moon
  
  

48. It can be inferred from the passage that (   ). 

• A、when one is in a bad mood, he or she may not work very well
  
  

• B、the best way to overcome a bad mood is to talk to oneself
  
  

• C、some drugs are more effective than physical exercises
  
  

• D、taking drugs is at the risk of being poisonous