The idiom "Wash dirty linen in public" means to publicly discuss personal or private matters that are usually kept confidential — especially arguments or family problems.
Let’s examine the choices:
(A) To criticise – Not specific to personal matters.
(B) To talk dirty things in public – Misleading and incorrect.
(C) To wash clothes – Literal, not idiomatic.
(D) Make personal quarrels public – Correct idiomatic meaning.