________ is an example of a formal letter.

The correct answer is Option (1) - A letter to an editor

Explanation:

• A formal letter is written for official, professional, or public purposes — such as to an editor, a principal, a manager, or a government officer.

• It follows a specific format (sender’s address, date, receiver’s address, subject, salutation, body, and formal closing).

Why others are incorrect:

• A letter to a friend →  This is informal, written in a personal tone.

• A letter to a relative →  Also informal, used for personal communication.

• A letter to one’s family →  Personal and informal as well.

 Hence, “A letter to an editor” is the correct example of a formal letter.