21. I failed in the job interview and only then _____ the importance of learning English well.
A. I realized B. I had realized C. did I realize D. had I realized
22. I would appreciate ______________ if you could come to my birthday party.
A. you B. this C. that D. it
23. The fields where crops used to be grown ________ for building now.
A. have used B. have been used
C. are being used D. are used
