Final answer:
Interjections that stand alone in writing are typically punctuated with an exclamation point, which signifies strong emotion or a sudden utterance.
Step-by-step explanation:
When writing, interjections that stand alone are generally punctuated with an exclamation point. For example, when someone expresses a strong emotion or calls to someone abruptly, they would use an exclamation point, such as in the phrases "Wow!" or "Hey!" This form of punctuation conveys the intensity or emotional impact of the utterance. In contrast, a period would denote a more matter-of-fact statement, a comma indicates a brief pause within a sentence, and a question mark is used at the end of a query.
Correct usage of these punctuation marks is crucial in conveying the intended tone and meaning of your writing.