Drag and drop the terms on the left to complete the concept map

Do you have a picture of the concept map? :)

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.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.