Unless the subject matter is considered common knowledge, citations are necessary when writing about:

The correct answer is: When writing about perhaps any given subject, it is crucial for the writer to consider the citations and credit that must be given to the sources they are using. Unless it is about common knowledge that is understood by all, then it wouldn’t be necessary to do so.

So, I don't know your options, but for any subject it is true that you must cite your sources!

Afine-grained igneous rock forms as a result of slow cooling.