Concept:The sentence tests whether the tense and phrasing correctly ask about a person's origin or nationality.Explanation:The question asks about nationality with “Are you an American?”. To match this meaning, the first part should be “Where do you come from?”. “Where are you coming from?” usually asks about the place someone is arriving from now, not their origin. So part (a) contains the error.Answer:The error is in part (a).