The given answer, inflammation, is the most suitable explanation because it is a common response of the body's immune system to infection or injury. Inflammation is characterized by redness, swelling, heat, and pain in the affected area. It is a natural defense mechanism that helps to isolate and eliminate harmful stimuli, such as pathogens or damaged cells. Inflammation can occur in response to various factors, including infections, injuries, autoimmune disorders, and chronic diseases. Therefore, considering the options provided, inflammation is the most relevant explanation.