Final answer:
A nail rusting is a chemical change since it involves the formation of new substances with different properties than the original materials. Therefore, the correct option is B.
Step-by-step explanation:
When a nail rusts, chemical change occurs. This is because rusting is the result of iron (Fe) reacting with oxygen (O₂) in the presence of water (H₂O) to form iron oxide (Fe₂O₃), which is commonly known as rust. This process involves a change at the molecular level, where new chemical bonds are formed, and the properties of the rust are different from those of the original iron and oxygen.