Answer:
C. By causing auxin to migrate in to the shaded portion
Explanation:
Auxin is the most important plant hormone involved in the apical growth of plant parts. Auxin is evenly distributed in a plant with a normal light condition, however, when a particular part of a plant is exposed to sunlight, that illuminated part contains less auxin. The hormone is transported to the shady part of the plant via diffusion.
This causes more auxin to be present in the shady part than the illuminated part, hence, the shady part experiences a faster and elongated growth. This elongated growth in the shaded portion of the plant causes it to grow towards the direction of the light, a process called PHOTOTROPISM.
