PLEASE BE QUICK 100 points Jamal has dissected a cow's eye and is studying how well the lens refracts light. He knows that a lens will refract, or bend, light toward a certain point behind it, known as the focal point.

He removes the lens from the eye and places it 20 cm from a single light source in an otherwise dark room.

How could Jamal measure the distance between the lens and its focal point?
A.
He could hold a sheet of paper behind the lens, move it away from the lens until the light is focused on it, and then measure the distance between the paper and the lens with a ruler.
B.
He could use a ruler to measure the frequency, wavelength, and amplitude of the light waves that exit the back end of the lens.
C.
He could hold a sheet of paper between the light source and the lens, move it toward the light source until the light is focused, and then measure the distance between the paper and the lens.
D.
He could use a stopwatch to measure the time it takes light to travel from the light source, through the lens, and to the lens' focal point.