He narrows his eyes at her at the request. He wasn't expected to be quizzed on his knowledge of the elements. He remembers receiving a pamphlet on the subject, but he'd only briefly glanced over it. But don't elements in magic work the same way that they do in nature? Let's go with that. At least he knows what the seven elements are that a Red Mage can perform.

"Ice is strong against water, which is strong against fire, which is strong against wind, which is strong against electricity. The Light and the Darkness depends on the strength of the user. If they're equally strong they can cancel each other out." He finishes with a hint of a satisfied smile on his face. He might be totally pulling this out of his ass but at least it sounds plausible.