Which of the following could indicate a possible infection?

Redness in a body part can be a significant indicator of a possible infection. This redness, often referred to as erythema, typically occurs due to inflammation as a response to infection, injury, or irritation. When tissues become infected, they may swell and produce increased blood flow to the area, leading to visible redness. This is part of the body's natural immune response aimed at combating the infection.

In contrast, increased energy levels typically suggest good health rather than infection. A decrease in temperature often indicates that the body is not fighting an infection or may even be a sign of another medical issue. Rapid weight gain can be related to a variety of health conditions but is not a direct indicator of infection. Therefore, the presence of redness in a specific area is a much stronger clinical sign that warrants further evaluation for potential infection.