The correct answer is Option D Uphill transport.

This is because – Special proteins aid in the movement of molecules across membranes without the use of ATP energy in assisted diffusion. Because it would require energy input, assisted diffusion cannot promote net transport of molecules from low to high concentrations. When all of the protein transporters are in use, the transport rate achieves a maximum (saturation). Uphill transportation, on the other hand, is unrelated to aided transportation.