Which of the following is an example of a chemical change

The right answer is grilling a burger.

The other answers are physical changes (strumming a guitar , converting matter into energy , melting of copper).

The Maillard reaction is a set of chemical reactions that occur during cooking and that unfold the aromas of food. Maillard (1878-1936) worked on the reactions between amino acids and sugars in the 1910s and recorded his observations and results in his book Genesis of Proteins and Humic Matters. Action of glycerine and sugars on amino acids published in 1912.

The Maillard reaction occurs during cooking. It is partly responsible for the browning and unfolding of aromas. New molecules are formed from amino acids and some simple sugars. They combine in chains and the sets they form reflect the light in such a way that we perceive the surface of the food as brown.

if you listed your answers right then i believe your answer is b.