Which of the following is a sign of infection?

Fever, redness, increased discharge, and swelling are all classic signs of an infection occurring in the body. Fever is often the body’s response to an invading pathogen, indicating that the immune system is actively working to fight off the infection. Redness and swelling typically occur at the site of infection due to increased blood flow and the accumulation of immune cells responding to the infection. Increased discharge could also indicate that the body is trying to flush out microorganisms. Together, these symptoms form a clear picture of inflammatory processes associated with infections.

In contrast, increased appetite would typically not indicate an infection; rather, it's usually associated with good health or recovery. Improved mobility generally suggests healing or a positive response to treatment, not an indication of infection. Clear urine can signify adequate hydration and normal kidney function, but it does not provide evidence of infection, as urine can be clear even if an infection is present elsewhere in the body.