It was very kind of you to do the washing-up, but you _ it.

The correct answer is option number -D

Mustn't have done is the correct answer.

Mustn't have -Must is a modal verb,it adds meaning to another verb.

Mustn't we use to show possibility or necessity.

Must not -We use to talk about things we need to avoid doing or while telling someone to not do it.

Rest options are grammatically & contextual incorrect.

Hadn't to do -Had we use to indicate past things.Also hadn't to do is grammatically incorrect.

Might -We use might to show prediction, possibility, probability.

Ex- the Prime Minister might visit the town.

Here indicating possibility.

Might & hadn't is inappropriate because sentence is in the present tense.

Usage of didn't is not contextually correct.

Didn't have to do -We say didn't have to represent specific point of time that has already passed.

Only option `Mustn't have do' is grammatically & contextually correct.