The mold of Claviceps purpurea occasionally grows on grain, especially rye, and eating infected grain results in an illness called , which can cause headaches, vomiting, diarrhea, and gangrene of the fingers and toes.

the most logical answer would be a

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 would cause an increase of percipitation, though i could be wrong. so i would say b is the answer.