Final answer:
The Na+/glucose symport protein assists in indirect active transport by moving both Na+ and glucose into the cell, with glucose being transported against its concentration gradient.
Step-by-step explanation:
Secondary active transport is a type of active transport where the movement of one substance is coupled with the movement of another substance. An example of indirect active transport is the Na+/glucose symport, in which both Na+ and glucose are moved into the cell. The Na+/K+ ATPase pump on the basal membrane of a tubular cell constantly pumps Na+ out of the cell, creating an electrochemical gradient for Na+ to move into the cell from the tubular lumen. The Na+/glucose symport protein on the luminal surface assists in moving both Na+ and glucose into the cell, with glucose being transported against its concentration gradient. Therefore, the answer is D) Na+/glucose symport.