When two continental plates collide, sometimes one plate slides beneath the other in a process known as subduction. When one continental plate slides beneath another

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.

since there are no options posted i'll give you a few examples.

a dolphin's flipper, bird's wing, cat's leg.