Historical is an adjective (adv) in the sentence "The United States has hundreds of important historical sites, many of which have been designated national monuments."
<h3>Define adjective.</h3>
A term that often modifies a noun or noun phrase or characterizes its referent is known as an adjective in linguistics (abbreviated adj). Its semantic function is to modify the noun's information. Although historically they were grouped alongside nouns, adjectives were once thought to be one of the major speech elements of the English language. Many words that were once categorised as adjectives, such as the, this, my, and others, are now classified independently, as determiners.
To know more about conjunction visit:
brainly.com/question/11860695
#SPJ4