Which type of transport is used to move a molecule from a region of low concentration to a region high concentration?

Active transport is the process in which molecules or particle move against the gradient i.e from regions of lower concentration to the regions of higher concentration. In bio process, molecules undergoing active transportation usually move by utilizing the energy produced during respiration. The active transportation usually takes place when some molecules are at high concentration inside the cell but they are required by the organism, then carrier protein moves these specific molecules through the process of active transport.

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.