During cellular respiration, when pyruvic acid is created (particularly in glycolysis), the main products are 2 ATP molecules and 2 NADH molecules per glucose molecule, along with the production of pyruvic acid. However, your question pertains to the overall process, not just glycolysis.
In the context of the complete cellular respiration process (which includes glycolysis, the citric acid cycle, and oxidative phosphorylation), additional products include water and carbon dioxide.
But focusing specifically on what is produced directly as a result of glycolysis (where pyruvic acid is formed), the correct answer from the options you have provided is:
heat
This is because energy transformations in biochemical reactions often release heat as a byproduct.