Answer: Option (d) is the correct answer.
Explanation:
When a substance is present in a solution then it is represented by a symbol "(aq)" which means aqueous.
When a substance is present in a solid state in a solution then it is indicated by a symbol "(s)" which means solid.
When a substance is present in a liquid state in a solution then it is indicated by a symbol "(l)" which means liquid.
When a substance is present in a gaseous state in a solution then it is indicated by a symbol "(g)" which means gas.
Hence, we can conclude that in a chemical equation, (aq) symbol should be used to indicate that a substance is in solution.
