. I just don't understand_____________ that prevents so many Americans from being as happy as one might expect.
106. Where are my keys? They seem to have ____.
105. The waters of this great lake, which is also the world's deepest, have been ____ by waste from a chemical factory.
104. --- What do you do in the theatre? --- I ____ plays.
103. Can you _____ the difference _____ American English and British English?
102. In the minority nationality the custom doesn’t ____ and has come down from generation to generation.