Question

demodex mites live in the eyebrows, eyelashes and other hair follicles on the faces of about 65% of people, because we produce sebum... their favorite treat. demodex eat the sebum, but don’t bother their humans. (do your eyebrows itch yet?)
mutualism
commensalism
parasitism

Explanation:

Mutualism is when both species benefit. Commensalism is when one species benefits and the other is neither helped nor harmed. Parasitism is when one species benefits at the expense of the other. Demodex mites benefit from eating sebum produced by humans, and humans are neither helped nor harmed. So it's commensalism.

Answer:

B. commensalism