Many fast-food restaurants, including Burger King, McDonald's, and Wendy's, no longer use polystyrene containers (which do not degrade as quickly as paper in a landfill) for packaging their products. Rather, these firms wrap their burgers in recycled paper wrappers, containers, and bags, usually clearly marked as such. These fast-food restaurants are practicing __________ a) triple-top line marketing. b) green marketing. c) consumerism. d) an ecological code of ethics. e) cause marketing.