Concept:New substances are formed only in chemical changes.
Explanation:Burning of wood is a chemical change. Wood reacts with oxygen to form ash, carbon dioxide and water vapour. These are new substances.
Rusting of an iron nail is also a chemical change. Iron reacts with moisture and oxygen to form rust, which is a new substance.
Heating water into vapour is a physical change. Water changes from liquid to gas, but its chemical composition remains
H2O. No new substance is formed.
Therefore, only I and II result in the formation of a new substance.
Answer:B. I and II only