Give one environmental challenges facing humans for either the carbon, nitrogen, or phosphorus cycle.

Answer is in the file below

cutt.ly/zxt1ipy

oak trees? ? what was listed

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.