51.(      )

17. The park is to a city (   ) the lung is to man' s body. 

• A、as
  
  

• B、that
  
  

• C、which
  
  

• D、what
  
  

36. Mr. Brown (   ) . 

• A、works on his own in a bank
  
  

• B、 lives in a bank and works on his own
  
  

• C、lives by himself and works in a bank
  
  

• D、lives with his sister and works by himself