Final answer:
The most appropriate verb to fill in the blank is 'estoy'.
Step-by-step explanation:
The most appropriate verb to fill in the blank is estoy.
The correct sentence is 'Yo estoy barriendo el piso'.
'Estoy' is the first person singular form of the verb 'estar' in the present tense, which means 'to be' in English.
Learn more about Spanish verbs