You are right about using El Indefinido Progresivo as well. There is nothing specific in the hint that restricts it to just the Imperfecto Progresivo. We will change the hint to "Conjungate in El Imperfecto Progresivo", not "El Pasado Progresivo".
I hope this helps.
Note that we have a lesson contrasting these two tenses. Here it is in case you haven't come across it. :))
El Imperfecto Progresivo vs El Indefinido Progresivo
Sign in to submit your answer
Don't have an account yet? Join today
Test your Spanish to the CEFR standard