Which of the following is considered a type of biological evidence?

Blood is classified as a type of biological evidence because it originates from a living organism. It contains DNA that can be analyzed to identify individuals or establish associations between a suspect and a crime scene. Biological evidence like blood is crucial in forensic investigations as it can provide definitive proof linking people to a specific incident through genetic information.

In contrast, the other options do not fit the criteria for biological evidence. Paint fragments and gunpowder residue are considered chemical evidence, as they result from materials used in various contexts (such as paint in objects or gunpowder from firearms) but do not contain organic material or DNA. Footwear impressions, while they may provide critical information regarding a suspect's movements, are classified as physical evidence rather than biological, as they relate to the impression and not to a biological substance.