Swiftly : Adverb :: Beautiful : ? Complete the analogy.

The relation is a word : the class of words in grammar to which it belongs. 'Swiftly' tells in what manner an action is done, which makes it an adverb; 'beautiful' tells what a person or thing is like, which makes it an adjective. None of the distractors describes anything — a noun names a person, place or thing, a verb states what is done or what is, and a pronoun merely stands in the place of a noun already named.