Me,

suppose you have two bar magnets. one has it's north and south poles marked, but the other one does not. describe how you could use the first magnet to identify the poles of the second magnet. explain

Put the marked magnet up to each side of the unmarked one. if they attract they are opposite -north attracts south, south attracts north- if they repel -forcefully push away- from each other they are the same -north and north, or south and south. once you have done that you can label the poles correctly.