The model above shows a cell moving a substance into the cell using a protein to facilitate the transport. Which
substance is most likely being transported through the membrane with this method?

there is no diagram and it may be cytoplasm

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

most community's take hundreds of years to become stable