which of the following particles can pass through the atp synthase channel?

The particle that can pass through the ATP synthase channel is protons (H+ ions). ATP synthase functions as a proton channel that allows protons to flow down their electrochemical gradient from the intermembrane space back into the mitochondrial matrix (or from the thylakoid lumen to the stroma in chloroplasts). This proton flow through ATP synthase drives the rotation of the enzyme's subunits and the synthesis of ATP from ADP and inorganic phosphate. Other molecules like ATP, ADP, or inorganic phosphate do not pass through the ATP synthase channel; only protons can move through it. Therefore, the correct answer is protons.