Answer:
adjective.
Explanation:
An adverb is one of the parts of speech which is used to <em>modify a verb, </em><em>adjective</em><em>, and another adverb</em>. The purpose of an adverb is to tell the reader about the hows, where, and whens of an action or its quality.
<u>An adverb is easily identifiable as most of it usually ends with </u><u><em>-ly </em></u><u>such as kindly, silly, fortunately, etc.</u><u><em> </em></u><u>Some words plays double role of both being an adverb and adjective. Such as fast, late, most, etc</u>.
So, from the given options the correct answer is that the word an adverb modifies is <em>adjective</em>.
An example of adverb modifying adjective-- 'This book is <em>very </em>interesting.'
Thus option second is correct.