You have three boxes, all containing fixings/fasteners, and all labelled incorrectly. You must get the labels right on all 3 boxes, the labels which read:
Box 1 – Nails
Box 2 – Screws
Box 3 – Nails & Screws
To get the information needed to move the labels to the correct boxes, you may remove a single item from one of the boxes, examine it, and you must then move the labels to the correct boxes. You may not look into the boxes, nor pick them up and shake them, etc. etc. etc.