The level in the biosphere that includes abiotic factors a. community
b. ecosystem
c. population

Generally, the ecosystem is the lowest level of organization that is considered to include nonliving factors. So that would mean that ecosystems, biomes, and the biosphere include abiotic factors

what have fossils ever done for you

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.