Which of the following is an appropriate way to close a formal letter?

Closing a formal letter typically requires a tone that reflects professionalism and respect for the recipient. "Yours truly" is commonly used in formal correspondence, which makes it an appropriate choice for closing a formal letter. This phrase conveys sincerity and maintains a respectful distance, suitable for professional contexts where a formal relationship exists.

In contrast, other options such as "Best wishes," "With love," and "Cheers" are more casual and affectionate closings. "Best wishes" can be seen as a friendly but informal ending, best suited for less formal communication. "With love" is explicitly personal and is generally reserved for intimate relationships. "Cheers" is casual and friendly, making it inappropriate for formal correspondence. Thus, "Yours truly" is the best choice for maintaining a formal tone and is widely accepted in professional letters.