Final answer:
An elevated body temperature is a sign of an infection, indicating a bodily response to create a less favorable environment for pathogens.
Step-by-step explanation:
The sign of an infection among the options provided is d) Elevated body temperature. An elevated body temperature, or fever, is often a response to infection as the body increases its temperature to create an environment that is less favorable for pathogens. In contrast, a normal body temperature and decreased white blood cell count typically do not indicate an infection. C-reactive protein levels increase in response to inflammation, so reducing levels would not be a sign of an ongoing infection.
In the context of infections, when the body is exposed to pathogens like bacteria or viruses, one way it responds is by increasing the number of white blood cells to fight off the invaders. This is a form of positive feedback, as the increase in pathogens leads to an increase in white blood cells to combat the infection. Furthermore, among the cardinal signs of inflammation, fever itself is not one; instead, redness, heat, and swelling are typical indicators of inflammation.