Compare the position of the frog's eyes with the position of human eyes

Eye placement probably evolved for different reasons in different groups of animals. 

Frogs have a much larger field of view than humans, due to the placement of their eyes. The eyes, situated on the top and sides of the head, allow them to see almost 360 degrees around them (which helps for a species that can’t turn its head). So the frog can see prey and preditors on both sides of its body with ease.

Human is a predator, they have forward facing eye instead of side eye. Forward facing eyes allow for binocular or stereoscopic vision, which allows an animal to see and judge depth. Predators need this depth perception to track and pursue prey.

The answer should be a

Spherical shaped cell might increase the surface area and decrease the volume.