Q: Fact 1: Lung cancer is most often caused by exposure to tobacco smoke. Fact 2: Tobacco smoke contains tar. Given the two facts above, lung cancer is most often caused by exposure to?

Pick your answer from: (1). DDT; (2). UV; (3). methane; (4). tar; (5). CFCs; (6). vapor; (7). SO2; (8). carbon dioxide;
A:
(4).