Answer:
B. Optional
Explanation:
A comma can be defined as a punctuation mark that is typically used for indicating a break in elements of a series or list in a sentence. Also, it's used to indicate the shortest pause in a sentence.
In the English language, conjunction can be defined as an English word that is typically used for connecting two or more clauses, words, phrases, or sentences. Some examples of conjunction are but, and, although, because, or, yet, etc.
When there are three or more items (elements) in a series, the final comma before the conjunction (and, or, nor) is optional.
