15.You may ________ the textbook if you don’t know the answer to the question.
--- What made Julia so unhappy? --- ________ her new bike.
Only after ___ your homework _________ watch TV.
She ____ an old friend of hers yesterday while she was shopping at the department store.
All possible means ____, but nothing can prevent the buildings ____.
Gun control is a subject _________ Americans have argued for a long time..