When One Plant Is Shaded by Another, Why Is the Ratio

When one plant is shaded by another, why is the ratio of far-red to red light increased compared to an unshaded plant?

A) Phytochrome in the taller plant absorbs most of the red light.
B) Auxin absorbs mostly far-red light.
C) As light passes through the leaves of the taller plant, most of the red light is absorbed by chlorophyll.
D) Far-red light mostly reflects off the surface of the soil while red light is mostly absorbed.