Physiology Which substance is most likely to increase in the rods of the retina when the light is turned on? A Cyclic adenosine monophosphate (cAMP) B Cyclic guanosine monophosphate (cGMP) C Metarhodopsin II D Rhodopsin 💡 Explanation Which substance is most likely to increase in the rods of the retina when the light is turned on? ✓ Correct Answer: C. Metarhodopsin II