Final answer:
Larry is experiencing an allergic reaction to pollen, causing his immune system to trigger sneezing as a form of defense against a perceived threat. It is an innate immune response to expel the allergen from the body.
Step-by-step explanation:
Larry's constant sneezing in the park due to the presence of pollen is an example of his immune system's response to what it mistakenly perceives as a pathogenic threat. This response is known as an allergic reaction, where the immune system identifies a harmless protein (the pollen) as an invader. The sneezing is part of the body's innate immune response, an involuntary reaction where nerves in the nasal passage are irritated by the allergen, causing a forceful expulsion of air and mucus to expel the allergen from the body. Allergens such as pollen can cause symptoms including sneezing, runny nose, nasal congestion, and itchy, watery eyes due to the immune system's inflammatory response. In summary, in Larry's case, his immune system is exhibiting a form of defense against what it incorrectly deems a pathogen, resulting in the symptoms we associate with allergies.