Final answer:
In simplified letter style, a medical assistant should use the full block format, with formal language, appropriate business font, and aligned paragraphs without indentation.
Step-by-step explanation:
A medical assistant composing business correspondence in the simplified letter style should use the full block format. This professional style involves certain formatting requirements like everything being left-justified, the text being single spaced with double spacing between paragraphs, and a clear, easy to read business font such as size 12 Times New Roman or Arial. Important to note is that paragraphs are not indented in this format. The writing should be formal, employing formal language and avoiding contractions, colloquialisms, or text language like "u" for "you" or "r" for "are". The use of multiple fonts for emphasis is normally avoided in formal business correspondence to maintain professionalism.