How does one usually sign off a formal letter?

Choose the most appropriate answer:

Yours faithfully

The correct answer is Option (4) - Yours faithfully

The most appropriate sign-off for a formal letter is: Yours faithfully.

Yours faithfully is commonly used when the recipient's name is unknown (e.g., when addressing "Dear Sir/Madam"). It conveys professionalism and formality.
Your humble servant is outdated and rarely used in modern correspondence.
Yours lovingly and Your friend are informal and more appropriate for personal or friendly letters rather than formal communication.