Choose the correct option :
In a formal letter we write _________ sincerely.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → yours
A formal letter closes with "Yours sincerely" (or "Yours faithfully"). Yours is a possessive pronoun and is written without an apostrophe; at the start of the closing line it takes a capital letter.
Example: The letter ended with Yours sincerely, followed by the writer's name.
Complete sentence: In a formal letter we write yours sincerely.
Why the Other Options are Incorrect?
Option 1: Your — Incorrect. Your is a possessive adjective and must be followed by a noun (your letter); it cannot stand alone in the closing.
Option 2: your's — Incorrect. Possessive pronouns (yours, hers, ours, theirs) never take an apostrophe; "your's" is a spelling error.
Option 4: you — Incorrect. You is a personal pronoun; "you sincerely" makes no sense as a closing.
Contrast: yours (possessive pronoun, no apostrophe) stands alone; your (possessive adjective) must be followed by a noun.