What do you mean?

The first blank being adjacent to an adverb ("relatively") and the second being adjacent to an adverb ("relatively") and an adjective ("accurate"), suggests filling the blanks with adverbs. Adverbs are the only words that can modify an adjective or another adverb. Example: "people are seldom relatively highly accurate judges" However, the statement is actually false. It is indeed possible to fill the blank with words that are not adverbs: "people are seldom relatively such accurate judges" in which "such" is not an adverb (though it might seem like one).

the phrase __relatively__ accurate shows adv + adj so an "advert" as a noun can't be used there