Classify each of the following as either round or square shape: wheel, paper napkin, building block, ring, coin, ball, grid, bread, bubble, dice, hula hoop, window, stamp, earth, crossword, tambourine, bagel, keyboard key, cube, letter O.

Objects that have circular (round) shape include: bagel, ball, bubble, coin, earth, hula hoop, letter O, ring, tambourine, wheel.
Objects that have square shape include: bread, building blocks, crossword, cube, dice, grid, keyboard key, paper napkin, stamp, window.