The answer is photosynthesis.Photosynthesis occurs in the leaves of green plants. During photosynthesis, carbon dioxide and water are converted into glucose and oxygen using the energy of sunlight. The excess of glucose synthesized in photosynthesis is converted and stored as a starch.
I don't see any options. But, an error can occur if a DNA polymerase inserts an incorrect base.
The signal will start from the eyes. The message is carried by sensory neurons to the spinal cord. There, the "impulse" will transfer to motor neurons which will carry it to the brain. So in short:
Sensory neurons --> spinal cord --> motor neurons --> brain
