Grandma smiled and looked out of the window. It had been such a good day. Which of the following parts of speech best describes the underlined word in the sentence shown?

Interjections are words or phrases that express strong emotion or sudden bursts of feeling, often standing alone and not grammatically connected to other parts of the sentence. Examples include "wow," "ouch," or "hey." Since "and" does not convey emotion but rather connects actions, it cannot be classified as an interjection.

Prepositions are words that show the relationship between a noun (or pronoun) and other words in a sentence, often indicating direction, location, or time. Examples include "in," "at," and "under." The word "and" does not indicate any relationship between nouns or provide locational context, thus it cannot be a preposition.

Adjectives modify nouns by providing additional information about them, such as describing qualities or quantities. Examples include "happy," "blue," or "three." Since "and" does not describe a noun but rather connects actions, it cannot be classified as an adjective.