20. I _______ the dance performance many times, each giving me a new understanding.

　　　 A. watch　　　　　　　　　 B. watched　　　　　　　　 C. have watched　　　　 D. am watching

19. The economic impact study was conducted by a group of _______ selected MBA students at the University of Kansas.

　　　 A. especially 　　　　　　 B. specially　 　　　　　　 C. regularly　 　　　　　 D. potentially