Answer:
Acabo de bailar
Step-by-step explanation:
To tell someone what you just have done, you should use ‘acabo de bailar’. The word ‘acabo’ in this sentence means ‘I just danced’. The other sentences are in different tenses.
‘Estoy bailando’ is in the present form, it means you are dancing now. ‘Hace tres días que bailo’ means you are still dancing now and you started three days ago. And ‘Hace tres días que bailé’ means you danced three days ago.