Which quantity of o2 contains exactly 3.01 x 10^23 atoms? and you! not looking for answers, i am really stuck on this one

Three cards with holes are arranged in a straight line. a light is shined through the first card’s hole and travels through all three cards. what does this tell you about light rays? a) that light is reflected b) that light is refractive c) that light travels in a straight line d) that light does not travel in a straight line