(2) Metal materials include metal and alloy, so the metal materials are wire mesh cover and Fe-Cr-Al electrothermal alloy, the organic synthetic material is plastic, and the quartz tube is inorganic nonmetal material;
(3) Fossil fuels include coal, oil and natural gas, which are non-renewable energy sources; SO2 emitted by coal combustion is one of the gases that form acid rain, and human beings not only rely on the combustion of fossil fuels to obtain energy, but also have other new energy sources.
So, the answer is: (1) a; ? (2)③; (3) natural gas; C.