How is the production of mercury from burning coal an environmental hazard? a. high concentrations of mercury in the air leads to global warming. b. mercury in water systems is transformed through biological processes into a substance that is toxic to animals. c. mercury combines with other coal emissions in the air to produce ozone. d. all of the above

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 think it’s c but i might be wrong. if i am let me know! have a good rest of your day as well!

the answer would be   10%