A chemical change is defined as a reaction that occurs and end up with a change in the components involving the reaction, a change in the chemical formula, and not just in the physical state of the compound (for example, the compound going from liquid to frozen). In our question, we have letter D as being the only chemical change, because rusting of metals, like iron, is an oxidation reaction, in which iron metal becomes iron oxide, therefore a chemical change. Answer letter D
