Which of the following is true about chiggers?

Chiggers are indeed parasites that interact with their hosts by injecting a secretion into the skin. When chiggers bite, they do not actually feed on blood; instead, they secrete enzymes that break down skin cells, allowing them to feed on the liquefied tissue. This process can cause intense itching and discomfort, which is commonly associated with chigger bites.

In terms of the other answer choices, while it's true that chiggers can cause irritation and discomfort, they are not known to transmit diseases. Their physical characteristic as arachnids means they do indeed have eight legs during their active, parasitic stage, but the key factor that highlights option B is the mechanism of their feeding process, which is distinct and significant. Additionally, chiggers are not beneficial to human health; they are considered pests due to the irritation they cause. Hence, the focus on their action as parasites through the injection of secretion underscores the truth of option B.