In the Late 1870s,Charles Darwin and His Son Francis Discovered

In the late 1870s,Charles Darwin and his son Francis discovered that if the tip of the grass was covered,phototropism did not occur,even though the rest of the grass was exposed to light.However,if the rest of the plant was covered and only the tip exposed to light,the grass bent a few centimeters below the tip.How could light striking the tip of the grass cause bending a few centimeters from the tip?

A) The light must be striking the cells that bend as well.
B) A hormone must be carrying the response from the tip to the site of bending.
C) The bending must start at the tip and move down the entire blade of grass.
D) Bending is independent of the source of light.
E) The light is being transmitted from the tip to cells at the site of bending.