You are presented with the question "What do humans use to see an image?" and the following answer choices: 
- keratin
 - light
 - heat
 - fibers
 - calcite
 - mussels
 - photons
 - Neuron.

Now knowing that when light enters the eye through the pupil , that light falls on the retina and humans use both eyes to see a single image, choose the best answer.


 

  light       