Not going through the lessons, coming to the sentence in the test cold, "costume" could be any translation of costume. "Custom" included. One shouldn't have to know your specific translation (which leads me to believe you just have a handful of stock translations per sentence, and don't actually do any translation on the back end).
Why is 'have' translated as 'abbiamo' and not 'hamo' or something (sorry if it's not right, it probably isn't). But can anyone explain why you use 'abbiamo'?
"Noi abbiamo" means, "We have." When first learning a verb what I often do is click on the verb in the question and then click on the "Conjugate" button. "Io ho" means "I have," so that would be wrong for this question, for example. I hope that helps!