_海南成考网

The reason why some professors ask students to make presentations and lead discussions is that____．

• A、these professors are often not well prepared before class
  

• B、these professors want to stress“doing”

• C、these professors want to test the students’abilities

• D、these professors are not wiHing to teach theory

Only then____that she had made a mistake．

• A、she realized
  
• B、did she realize
  
• C、had she realized
  
• D、she had realized

53__________ ?