"Un día ellas lo empezaron a repetir."
I suppose they will say 'comenzar' is to begin and 'empezar' is to start! In English, though, it surely is the same? I've now failed this section three times...and to lose a heart for 'began/started' is making me scream!!! Aaaarrgghhh!
I don't think so! Empezar, i believe, is ALWAYS followed by 'a' when another verb is to be used.
I finally got this one right and for anyone else who isn't sure why the 'a' is required. We have a conjugated verb followed by an infinitive which requires in this case an 'a' to link them or in other cases a 'de'. The real challenge is memorizing which one to use.