The answer is A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
Sodium ions are necessary for regulation of blood and body fluids, transmission of nerve impulses, heart activity, and certain metabolic functions. Physiologically, it exists as an ion in the body. Sodium is needed by animals, which maintain high concentrations in their blood and extracellular fluids, but the ion is not needed by plants.