Part A - The glucose-sodium cotransporter

the glucose-sodium cotransporter in animals, Na + moves back into the cell down its electrochemical gradient, providing the energy for glucose to move into the cell against its concentration gradient.

It makes sense css glucose is cotransported with Na + ions

In cotransport, the energy required to move one solute against its concentration or electrochemical gradient is provided by an ion moving into the cell down its electrochemical gradient.