Final answer:
Matches are classified as a flammable solid because they produce a combustion reaction causing a chemical change when ignited.
Step-by-step explanation:
The student's question asks about the classification of matches in terms of their flammability. Matches are an example of a flammable solid. When you slide the match head along a rough surface, you initiate a combustion reaction that produces energy in the form of heat and light. This reaction is a chemical property of the substance involved, as it involves a chemical change where the reactants (the match head materials and oxygen in the air) are transformed into new products such as carbon dioxide (CO2) and water (H2O), releasing heat in the process. Therefore, the correct answer to the question is C) flammable solid.