Final answer:
The correct form of 'tout' in this sentence is 'toute', agreeing in gender and number with the feminine singular noun 'robe.'
Explanation:
Tout needs to agree in gender and number with the noun it describes. In this case, since 'robe' is feminine singular, the correct form is toute. The sentence should read: 'Regarde ce que tu as fait. Ma robe est toute sale maintenant!'
Learn more about agreement in French grammar
