Which of the following helps to identify the presence of an infection?

The presence of pus formation is a strong indicator of infection. Pus is a thick fluid that usually consists of dead white blood cells, bacteria, and tissue debris that accumulate at the site of infection. When the body detects an invading pathogen, such as bacteria, the immune system responds, leading to inflammation and the accumulation of pus. Its presence signifies that the body is actively fighting an infection, which can be crucial for identifying the need for treatment.

In contrast, a clear wound might suggest a lack of infection, and swelling without redness does not necessarily indicate an infection either, as it can occur for various reasons, including inflammation that isn't infectious. Similarly, a stable body temperature generally suggests that there is no ongoing systemic infection, as fever is often a response to infection. Thus, the clear signs of pus formation provide a definitive clue in diagnosing an infection.