Final answer:
A correct complimentary closing for a letter from a medical office must be professional and polite. 'Sincerely' and 'Thank you' are standard closes for such letters, while closes like 'Yours truly' may not always be suitable.
Step-by-step explanation:
When closing a letter from a medical office, the complimentary closing should be professional and courteous. “Sincerely” and “Thank you” are standard and accepted closes for such letters. In a professional context, it's important to maintain formality, so closes with a more personal tone, such as “Yours truly”, might not always be appropriate depending on the context and relationship with the recipient. Typically, you would include the complimentary close, then leave space for a signature, and type your full name below the signature space. The closing of a letter is critical as it not only marks the conclusion but also provides a last impression of formality and professionalism.