**Core Concept**
The absorption of glucose from the gut into intestinal mucosal cells is coupled to the sodium-potassium pump (Na+,K+ ATPase), a process known as secondary active transport. This mechanism is essential for glucose absorption in the small intestine. In contrast, the movement of glucose from the intestinal epithelial cells into the submucosal bloodstream occurs through facilitated diffusion, a form of passive transport.

**Why the Correct Answer is Right**
The sodium-glucose cotransporter 1 (SGLT1) is responsible for the absorption of glucose from the gut into intestinal mucosal cells. This cotransporter uses the energy generated by the sodium gradient established by the Na+,K+ ATPase to drive the uptake of glucose against its concentration gradient. As a result, the absorption of glucose is tightly coupled to the activity of the Na+,K+ ATPase. On the other hand, glucose is transported from the intestinal epithelial cells into the submucosal bloodstream through facilitated diffusion, which is a passive process that does not require energy input.

**Why Each Wrong Option is Incorrect**
**Option A:** This statement cannot be true because the movement of glucose from the intestinal epithelial cells into the submucosal bloodstream is not coupled to the Na+,K+ ATPase. Instead, it occurs through facilitated diffusion.
**Option B:** This statement cannot be true because the absorption of glucose from the gut into intestinal mucosal cells is not a passive process. It is actively coupled to the Na+,K+ ATPase through the sodium-glucose cotransporter 1 (SGLT1).
**Option C:** This statement cannot be true because the movement of glucose from the intestinal epithelial cells into the submucosal bloodstream does not require energy input. It occurs through facilitated diffusion, which is a passive process.
**Option D:** This statement cannot be true because the absorption of glucose from the gut into intestinal mucosal cells is not a passive process. It is actively coupled to the Na+,K+ ATPase through the sodium-glucose cotransporter 1 (SGLT1).

**Clinical Pearl / High-Yield Fact**
The sodium-glucose cotransporter 1 (SGLT1) is responsible for the absorption of glucose from the gut into intestinal mucosal cells. This cotransporter is inhibited by phlorizin, a plant-derived compound that is used to study glucose absorption in the gut.

**Correct Answer:** C.

✓ Correct Answer: B. Free glucose levels in the lumen of the intestine can never be higher than levels in intestinal cells