Which of the following is a possible symptom of an upper respiratory tract infection?

In the context of upper respiratory tract infections, increased nasal obstruction and discharge is a common symptom. Upper respiratory tract infections, such as the common cold or sinusitis, often lead to inflammation of the nasal passages and sinuses. This inflammation can result in swelling, which causes nasal obstruction. Additionally, as the body responds to the infection, it produces excess mucus, leading to nasal discharge. This symptom set is typically what patients experience during such infections.

While other symptoms like high fever and cough with mucous production can occur, they are more characteristic of lower respiratory infections or other conditions rather than being primary indicators of upper respiratory infections. Allergic reactions, though potentially presenting with nasal symptoms, are not classified under upper respiratory infections, as they are not caused by pathogens but rather by immune responses to allergens. Thus, the correct choice accurately reflects a core symptom associated with upper respiratory infections.