Concept: A tertiary amine has all three hydrogen atoms of ammonia replaced by carbon groups.Explanation:In (C6H5)3N, the nitrogen atom is bonded to three phenyl groups, C6H5.Since all three bonds are to carbon atoms and none are to hydrogen, the amine is tertiary, denoted as 3∘.All three groups attached to nitrogen are aromatic phenyl rings.Thus, the compound is aromatic and not mixed, because mixed amines contain at least one aliphatic group.Therefore, (C6H5)3N is a 3∘ aromatic simple amine.Answer: Option C: 3∘ aromatic simple amine.