22. a. worry b. enjoy c. practice d. visit
23. a. corner b. opinion c. literature d. household
24. a. attention b. party c. program d. physics
25. a. geography b. memory c. difference d. subject
26. a. entertain b. remember c. improve d. decide
27. a. scientific b. impossible c. mathematical d. educational
28. a. determine b. obtain c. harbour d. award
29. a. atomic b. tragic c. extreme d. professional
30. a. radium b. tutor c. research d. institute
31. a. mature b. difficult c. brilliant d. physical