What a shame you didn't go to the airport to see Andrew off. You          there. You have been close friends for years after all.                   

A. might have been  B. would have been  C. should have been   D. must have been

What a shame you didn't go to the airport to see Andrew off．You ________ there．You have been close friends for years after all．

1. A.
   might have been
2. B.
   could have been
3. C.
   should have been
4. D.
   must have been