Which of these is a benefit of surface mining? a. runoff from surface mines can pollute local watersheds. b. accidental release of surface-mine waste can pollute waterways. c. surface mines change the environment where they are located. d. surface mines allow humans to obtain useful minerals.

The correct answer is option D, that is, surface mines allow humans to obtain useful minerals.  

Surface mining comprising open-pit mining, strip mining, and mountaintop removal mining refers to a wide classification of mining in which rock and soil superimposing the mineral deposit, are withdrawn, in comparison to the underground mining, in which the covering rock is left in location, and the mineral is withdrawn via tunnels of shafts.  

sand 60

clay 10

silt 30

sandy loam should be dominated by the sand. as the amount of sand increased, the amount of slit needed to anchor the plants' roots to the sand will also be increased. even though the amount is very little, 10% part of clay is still necessary for proper oxidation.