Translation:The owl went to a concert with its friends.
Not saying I am right, but because the oral statement sounded so much like (el búho fue al concierto con sus amigos) unless I slowed it up it was very hard to distinguish the difference between a un and al. Though the context would not be loss in an actual conversation, you would need a slow speaking person to tell the difference to me.
This is an odd one for native English speakers and brings out some if the idiosyncrasies of the english language. At least in the US. "It" generally refers to an object or thing. In cases like this it's more common to call the animal a he or she irregardless of what the gender actually is.
In this exercise I had the "choose the right words" from the selection below. I didn't pay close enough attention and selected "friends' ", not "friends". My screen isn't as clean as new and I didn't notice the VERY SMALL apostrophe on "friends" and I was marked wrong. That's tricky and sneaky! LOL.