Concept map for about forms of transport

Try to ask your question with more clearer way. Because i cannot understand it accurately.

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.

it takes hundreds of years to become stable.

if you have another question lmk.