Name 3 ways that the simulation shows you that the equation is balanced

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

Can someone me with 3 and 4 plz. this is for masteries test.

What type of matter is made of only one kind of atom