A luminal cell membrane Na+ channel is the main pathway for Na+ reabsorption in:

Ans D. Collecting duct principal cellsNa+ reabsorption by collecting duct principal cells occurs via a Na+ channel called ENaC (epithelial sodium channel). Na+ reabsorption in proximal tubule cells is coupled to transport of solutes via cotransport (e.g., Na-glucose) and antiport (e.g., Na+/H+ exchanger) mechanisms. Na+ reabsorption in the thick ascending limb involves a Na-K-2Cl cotransporter and, in the distal convoluted tubule, a Na-Cl cotransporter. Collecting duct intercalated cells are primarily concerned with acid-base, not Na+, transport.