Which of the following is an acute disorder affecting the lungs?

Anaphylactic reactions are severe, systemic allergic responses that can affect multiple organ systems, including the lungs, but they are not classified as a lung-specific disorder. While they may cause respiratory symptoms, they are primarily an acute allergic reaction that requires immediate medical attention and is not limited to lung pathology.

Hay fever, or allergic rhinitis, involves inflammation of the nasal passages due to allergens and primarily affects the upper respiratory tract. Although it can cause respiratory symptoms, it is not considered an acute disorder of the lungs themselves but rather a seasonal allergic reaction that does not typically lead to acute lung dysfunction.

Emphysema is a chronic obstructive pulmonary disease (COPD) characterized by long-term damage to the lungs and is progressive in nature. It does not present as an acute disorder; instead, it results in gradual tissue destruction and reduced lung function over time, making it distinct from acute respiratory conditions like asthma.