Final answer:
OPTION B.
A decrease in aquaporins would most likely lead to decreased activity of osmosis, which relies on these water channels for the facilitated diffusion of water across cellular membranes.
Step-by-step explanation:
If a cell is found to have fewer aquaporins than normal, this would most likely lead to decreased activity of osmosis, which is the process of water movement across cellular membranes from an area of lower solute concentration to an area of higher solute concentration. Aquaporins are integral to the process of facilitated diffusion of water. Therefore, a deficiency in aquaporins would impair the cell's ability to balance water effectively, affecting osmotic balance. While both facilitated diffusion and passive diffusion allow for the movement of substances across the membrane, the lack of aquaporins specifically impacts the rate at which water can move, thus impacting osmosis more directly than diffusion of other solutes or ions.