Which part of speech is the underlined word?
eek! there's a mouse!
a.
noun
b.
adverb
c.
conjunction
d.
interjection
eek! is the underlined work : )

D. interjection.

An interjection is a word used to state emotion, whether scared, angry, or excited, and is usually placed at the beginning of a sentence.

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!

The answer is most likely d