In which aspects do the nanotechnology improves enhanced oil recovery(eor)?

Nanotechnology helps to improve viscous fingering and the nano-particles can transmit through nanopores of sandstone which helps to increase the recovery by decreasing the surface tension between oil and water. The pore spaces are very fine so water molecules cannot penetrate through all of them in order to push the oil. This is why the nano-particles such as iron (Fe) and Silicon (Si) are used with distilled water. These particles can easily move through the interconnected pores and thereby pushes the oil to move out of it. It is a widely accepted concept in Enhanced Oil Recovery (EOR).

the answer is "c" im pretty sure.