Which of these is an example of an ectoparasitic relationship

The correct answer is B.

A tick living in animal’s fur coat

An ectoparasitic relationship is a kind of parasitism in which the parasite exists outside the host’s body, this is the opposite of endoparasitism wherein the parasite lives inside the body of the host.

An ectoparasite is a parasite that lives outside the host's body so the answer would be B. A tick living in animal’s fur coat. The tick is an example of ectoparasite since it lives in the outside part of the host's body which is the animal's fur.