The Main Reason That Gold Mining Is One of the Dirtiest

The main reason that gold mining is one of the dirtiest mining activities is that

A) only a few ounces of gold are recovered for each ton of rock mined.
B) many chemicals must be used to extract gold from the earth.
C) gold is only found deep underground.Digging tunnels creates a lot of dirt.
D) gold is only found in remote areas so mining it contributes significantly to emission of carbon dioxide because of the distances that miners must travel.