Audio worked for me. And, be honest, how many people's first thought was to count the letters? It was mine. :-)
I was marked wrong for (correctly) putting the word 'Esperanto' in quotation marks. That's the first time I've been penalised by Duolingo for punctuation, which it normally ignores.
I think the system doesn't count quotation marks as punctuation. People have trouble where it will mark you wrong for NOT including quotation marks where the system expects it.
I wrote, "How many letters does the word 'Esperanto' have?" and it was marked incorrect. This strikes me as a grave injustice.