I believe it is the sagittal plane
<span>proton gradient</span> establishment
Chemiosmosis is the process that allows the diffusion of a
molecule or an atom through the membrane. Also, it is the movement of ions
across semipermeable membrane down their electrochemical gradients. In chloroplast,
chemiosmotic coupling is an important factor in ATP production through proton
gradient establishment.
If those are the optional answers, it's most likely sodium.
<span>The correct answer for is C. experimentation</span>