What unique characteristic is shared by all adult deer ticks?

The correct answer highlights the unique capability of adult deer ticks to transmit Lyme disease, which is a significant health concern. Deer ticks, also known as black-legged ticks, are particularly known for their role in the spread of this disease caused by the bacterium Borrelia burgdorferi. When an infected tick bites a human or animal, it can transfer the bacteria into the bloodstream, leading to various symptoms associated with Lyme disease.

While the other options may contain partial truths, they do not accurately represent a unique characteristic shared by all adult deer ticks. For instance, not all adult deer ticks have a distinctive red coloration; this coloration can vary based on factors like age and species. Similarly, adult deer ticks do not live exclusively in water; they are often found in wooded or grassy areas where they can attach to hosts for feeding. Additionally, adult deer ticks have four pairs of legs in total—two pairs in the juvenile stage (larvae) and four in the adult stage, which is characteristic of arachnids, not just ticks. Therefore, the ability to transmit Lyme disease distinctly identifies adult deer ticks as they pose a risk to human and animal health.