Asection through the left eyeball that produces equal right and left portions of the eyeball would be a section of the eyeball.

midsagittal

Explanation:

The eyeball is the structure of the human eye that is shaped like a globe, arranged in a bone cavity and protected by human eyelids. Outside there are six muscles that are responsible for eye movements, as well as three layers attached to each other for the purpose of seeing, nourishing and protecting the eyes. Among these layers, the so-called "midsagittal section" is responsible for producing equal portions to the right and left of the eyeball.

i think that d. wind is the answer.   i missed the question when i answered a. currents.

b.