What is a common complication leading to hospitalization due to flu?

The correct answer focuses on the common complications that can arise from influenza, which often lead to hospitalization. Common flu complications include pneumonia, bronchitis, sinus infections, and exacerbation of chronic health issues like asthma or heart disease. These complications can significantly worsen a patient's condition, making hospitalization necessary for more intensive medical care and monitoring.

In contrast, options like severe headache, joint pain, and stomach upset are symptoms that may accompany the flu but are not typically the direct complications that result in hospitalization. While these symptoms can be uncomfortable and impactful on daily life, they do not carry the same level of risk or severity as the complications listed in the correct answer. Thus, focusing on flu complications provides a clearer understanding of the potential dangers associated with the illness and why they can lead to a need for hospitalization.