Final answer:
The best description of the middle paragraphs in a direct approach letter is an explanation of details, where facts supporting the letter's purpose are provided in an organized manner.
Step-by-step explanation:
Of the following, the best description of the middle paragraph(s) of a letter using the direct approach is an explanation of details. In a direct approach letter, after the opening paragraph presents the main purpose of the letter concisely, the subsequent paragraphs should delve into the details. These middle sections explain why the purpose stated is important and provide supporting facts, while remaining succinct and logically organized. If the letter addresses multiple main points, each point typically corresponds to a separate body paragraph. This structure clarifies the letter's intent, leading up to the final paragraphs that restate the purpose, build goodwill, and may include a call to action.