Over time, sand dunes tend to migrate

It Migrate in the direction of the wind

A sand dune is known to be a hill, mount or ridge of sand that is found behind the beach and they are commonly affected by tides. Thus, sand dunes are formed over many years when the wind blows sand and such sand is trapped by beach grass or stationary objects. Furthermore, sand dunes usually protect inland areas from flood water, hurricanes, surges and waves action that can destroy properties. Also, they provide nesting habitats for array of organisms such as coastal birds.

its the cell wall and the they are unique to plant

the answer is d (apex) good luck : ))