Which of the following is an example of an interjection?

An interjection is a word or phrase that expresses a strong emotion or sudden exclamation, often standing alone or being inserted into a sentence. The option "Wow!" perfectly illustrates this definition as it conveys surprise or admiration. Interjections typically do not grammatically relate to the other parts of a sentence, which aligns with "Wow!" being an independent expression of feeling.

The other options do not fit the definition of an interjection. "Quickly" serves as an adverb that describes the manner of an action. "After" is a preposition that indicates a time relationship. "And" is a conjunction used to connect words or phrases and does not express emotion. These functions differ from that of an interjection, making "Wow!" the clear example of that part of speech.