The correct answer is option 1) i.e. Adjective. Explanation
Let us explore the options:
Adjective: Adjectives are words that describe the qualities or states of being of nouns or a word naming an attribute of a noun.
Noun: A word (other than a pronoun) used to identify any of a class of people, places, or things ( common noun ), or to name a particular one of these ( proper noun ).
Preposition: A word governing, and usually preceding, a noun or pronoun and expressing a relation to another word or element in the clause.
Adverb: A word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc.
From the above explanation, we can say that the adjective 'beautiful' is describing the quality of the noun 'vase'.