Analyze and answer the following case-based scenario:
Ravi is playing football on the school playground. After running continuously for a few minutes, he feels tightness in his chest and begins to breathe more rapidly. His face turns slightly red, and he starts sweating more than usual. His teacher explains that these changes are normal body responses during physical activity.
a. What causes Ravi’s increased breathing rate?
b. Which organ is primarily responsible for exchanging gases in his body?
c. Which structure prevents food from entering the respiratory tract while he breathes?