Bonjour
so we can't listen to the audio ...
BUT --> if you have the 'article partitif' au = à le ..
So it HAS to be followed by a masculine singular noun
à le bras = au bras
à le genou = au genou
à le dos = au dos
if it was followed by a fem. noun -------> à la
il a mal à la tête
elle a mal à la jambe
.....
AND if it was followed by a plural noun ---> aux
So now listen carefully to your audio, and you'll find out.. It has to be a masculine singular noun ..........
Où a-t il mal ?
Il a mal au + masc. noun ...........;