well, it's DEFINETLY not a noun, so A is OUT
B. - an adverb is a word that qualifies an adjective, verb, or other adverb word or word group, so that's out too
C- a word used to connect 2 simple sentences, so that's out too cos "Eek!" isn't really connecting anything, now, is it?
D- it is a word that will express emotion and "pause words" like "um, err, uh?" and is often used at the beginning of the sentence and "sounds" like an exclamation
So it is D!
"Eek!" is an interjection!