Mark: Plastic-foam cups, which contain environmentally harmful chlorofluorocarbons, should no longer be used; paper cups are preferable. Styrene, a carcinogenic by-product, is generated in foam production, and foam cups, once used, persist indefinitely in the environment. Tina: You overlook the environmental effects of paper cups. A study done 5 years ago showed that making paper for their production burned more petroleum than was used for foam cups and used 12 times as much steam, 36 times as much electricity, and twice as much cooling water. Because paper cups weigh more, their transportation takes more energy. Paper mills produce water pollution, and when the cups decay they produce methane, a gas that contributes to harmful global warming. So they are a worse choice. Which one of the following, if true, could Mark cite to counter evidence offered by Tina? ['The production and transportation of petroleum occasions serious environmental pollution, but the energy that runs paper mills now comes from burning waste wood rather than petroleum.', 'The use of energy for chain saws that cut down trees and for trucks that haul logs is part of the environmental cost of manufacturing paper.', 'Foam cups are somewhat more acceptable to consumers than paper cups because of their better insulating qualities.', 'Acre for acre, tree farms for the production of wood for paper have fewer beneficial effects on the environment than do natural forests that remain uncut.']