If something is described as "arcane," it is likely to be?

The term "arcane" refers to something that is known or understood by only a few; it often conveys a sense of obscurity, mystery, or complexity. When a subject is described as arcane, it implies that it is not only difficult to understand but may also involve specialized knowledge that is not readily accessible to the general public. This aligns perfectly with the notion of being obscure and mysterious, as it denotes an elite kind of knowledge that is not easily grasped by everyone.

The other choices do not capture the essence of the term. Something described as commonly understood would contradict the meaning of arcane by suggesting it is accessible to many people. Similarly, being well researched or clearly explained implies clarity and widespread understanding, which goes against the idea of obscurity inherent in the term "arcane."