A student conducted an investigation to study phototropism in grasses. The only difference between the control group and the experimental group was light conditions. The control group was provided full light, while the experimental group was shaded on one side. The diagrams show the average heights and positions of blades of grass in the investigation. Which statement best explains why the grass tips of the experimental group bent toward the light?
a) Water evaporated faster on the side of the plant having full light.
b) Light sensors in the grass tips stimulated a hormone in the shoot system.
c) The xylem in the root system absorbed more nutrients from the shaded side.
d) The side facing the light has a greater chance of absorbing carbon dioxide from the atmosphere.