It is intentional as far as I can tell... Duolingo does that with all its language courses... it's ok though, because it reveals the answer if you guess it wrong, and it just recycles the word at the end until you get it right... maybe it's part of Duolingo's teaching philosophy that you learn more from guessing wrong than just being told the answer
If the word is underlined, then you can tap on it to see the translation. You'll be able to do this the first Several Times a new word is presented. In fact the very first time a word is presented, it'll also be highlighted (a difficult to read languish-yellow color). Once you tap on it to see the translating, it'll turn black.
I think the solution to this is to make sure you tap on and listen to all of the multiple choice options that are presented to hear them all before selecting the correct one, even if you know the answer. In this case, the bag was an option (though not the correct answer) in a previous quiz or two.