17. It was on October, 1949 (   ) the People's Republic of China was founded. 

• A、that
  
  

• B、which
  
  

• C、till
  
  

• D、when
  
  

44. You shouldn't sit with your back towards the window because (   ). 

• A、the light is too bright
  
  

• B、the light is bad for your eyes
  
  

• C、you are in a dark room
  
  

• D、your book is in your shadow
  
  

52 .(    ).