Which of the following terms would best describe something common or unremarkable?

The term "mundane" is the most accurate choice for describing something that is common or unremarkable. "Mundane" specifically refers to things that are ordinary, dull, or lacking in excitement. It emphasizes the everyday aspects of life, suggesting that something is so common that it blends into the background and does not stand out.

In contrast, "novel" denotes something new or original, suggesting uniqueness rather than commonality. "Conformity" relates to the act of matching attitudes, beliefs, and behaviors to what is generally accepted, which does not specifically convey the idea of being common or unremarkable. "Prevailing" describes something that is widespread or dominant at a particular time, which can imply importance or preeminence rather than being ordinary or unremarkable. Therefore, "mundane" is the best word to encapsulate the idea of something that is commonplace and lacks distinction.