Is there a way to merge to arrays into one?

I am trying to set up a game using items in different categories and merge them into one. I.E. I have an empty array and several other arrays that hold categorized images (vehicles, animals, etc). At the start of the game, three random categories are chosen Is there a way I can merge these three categories (arrays) into the empty array? I tried using the Append node, but it seems to only be adding the first set to the empty one. Not all three.

You’ll have to append each of the 3 categories to the Empty array, one by one