16. I want everybody to listen __________. A. care                                B. careful                          C. careless                        D. carefully 18. Solar energy doesn't cause __________. A. pollution                         B. polluted                        C. pollute                          D. pollutant 19. Where __________ you go if you have a car? A. would                            B. have                             C. will                              D. did 20. Prevention is better than __________. A. treatment                       B. pills                             C. cure                             D. doctors