Here, we have analogous relation between two terms. Basically, it means that the terms "engineering" and "profession" are related in the same way as "yacht" and our mysterious term.
Engineering is one of many existing professions; it is only an example or a type. So, we now need to infer what is a yacht example of. Yacht is, of course a boat, relatively large in size, which means that the best fitting answer out of given options is "vessel".
