Which of the following is a symptom of the flu?

The symptom that stands out as a characteristic of the flu is a severe hacking cough. Influenza typically presents with a range of respiratory symptoms, including a cough that can be quite debilitating and persistent. This cough usually develops as a response to the virus affecting the respiratory tract.

Other symptoms of the flu often include fever, chills, body aches, and fatigue, alongside respiratory issues. While flu can sometimes cause a sore throat as well, it is usually not as prominent as the severe cough associated with the illness.

In contrast, itchy eyes and rash formation are more commonly associated with allergies or other conditions rather than influenza. Allergies and some skin reactions can lead to itchy eyes and rashes, which are not typical symptoms of the flu. This differentiation is crucial for accurate diagnosis and treatment.