Final answer:
The commonality between rusting of iron and browning of a banana is that both are chemical changes where the original substances react and form new products.
Step-by-step explanation:
The two changes that have something in common are rusting of iron and browning of a banana. Both of these processes are examples of chemical changes. In rusting, iron reacts with oxygen to form iron oxide, causing a color change and a change in the chemical composition of the material. Similarly, when a banana browns, it is due to the oxidation of certain compounds within it, resulting in a new, darker substance. These processes both produce new substances and are indicative of chemical reactions taking place.