49. Parents can find out what their kids will study next year by______. 

• A、doing math-related activities
  
  

• B、having a learning-filled summer
  
  

• C、reading the textbooks
  
  

• D、talking with the teachers
  
  

17. Everything changed ______ quickly that I almost had no time to think.

• A、such
  
  

• B、how
  
  

• C、as
  
  

• D、so
  
  

51.