45. The word "shades" in the passage means (   ) .

• A、 symbols
  
  

• B、examples 
  
  

• C、signs
  
  

• D、reminders
  
  

20. —I usually go to school on foot. 

—Why don't you (   ) by bus for a change?

• A、try to go
  
  

• B、trying to go
  
  

• C、to try to go
  
  

• D、try going
  
  

53 .(    )