Final answer:
The correct rule of hyphen usage is that hyphens and dashes are not interchangeable. Hyphens join words as modifiers, whereas dashes set off or emphasize content.
Step-by-step explanation:
The correct answer to which of the following is a rule of hyphen usage is D. Hyphens and dashes are not interchangeable. Hyphens are often used to join two or more words serving as a single modifier before a noun, thereby clarifying how multiple modifiers function. For instance, a well-known author uses a hyphen to indicate that the author is well known. In contrast, dashes are used to emphasize or set off phrases and can indicate a pause, a contrast, or a change of direction in the sentence. For example, when providing additional information, you could use a dash—much like this—to add emphasis.
Hyphens should not be seen as a tool to replace parentheses or brackets. Instead, hyphens help to clarify meaning and avoid confusion in compound modifiers. Dashes, parentheses, and brackets each have their distinct functions and cannot be used interchangeably with hyphens. Brackets are typically used for editorial comments, clarifications, or adding information, while parentheses enclose nonessential or supplementary information, de-emphasizing it rather than highlighting it as dashes do.