Fact 1: Coal is used for generating heat by burning. Fact 2: Like coal, petroleum is a fossil fuel. Given the two facts above, what is used for generating heat by burning?
Available choices: 1). Calcium carbonate; 2). carbon dioxide; 3). fossil fuels; 4). clouds; 5). peachleaf willow; 6). space; 7). calcite; 8). sunlight;
3).