Fact 1: Plants exhibit phototropism, or growing toward a light source.

Fact 2: Green plants use light as their primary energy source.

Given the two facts above, answer the question "Phototropism means growing toward what?" with the following options: 
- rocks
 - energy
 - retina
 - light
 - heat
 - The Sun
 - plants
 - sand


 

    light     