Which of the following indicates a deceased victim was alive at the time of a fire?

The presence of carbon monoxide levels in the blood indicates that a victim was alive at the time of a fire. Carbon monoxide is a toxic gas produced when fuels are burned incompletely, common in fires. If an individual inhales smoke containing carbon monoxide, it enters their bloodstream and binds to hemoglobin, displacing oxygen. The higher the levels of carbon monoxide found in the blood, the more likely it is that the victim was breathing in the smoke while alive.

While the other choices may provide context regarding the victim's condition or the fire's severity, they do not specifically indicate signs of life during the fire. For instance, pulmonary edema may be related to various medical conditions and not necessarily to fire exposure. The presence of soot in the lungs can suggest inhalation but is less definitive than carbon monoxide levels. Burn injuries on the body indicate that a victim was exposed to flames; however, they do not confirm that the individual was alive during the fire since it is possible to be burned post-mortem.