The answer would most likely be A.Surface mining, including strip mining, open-pit mining and mountaintop removal mining, is a broad category of mining in which soil and rock overlying the mineral deposit (the overburden) are removed. In contrast to underground mining, in which the overlying rock is left in place, and the mineral removed through shafts or tunnels.
Surface mining began in the mid-sixteenth century[1] and is practiced throughout the world, although the majority of surface coal mining occurs in North America.[2] It gained popularity throughout the 20th century, and surface mines now produce most of the coal mined in the United States.[3]
In most forms of surface mining, heavy equipment, such as earthmovers, first remove the overburden. Next, huge machines, such as dragline excavators or Bucket wheel excavators, extract the mineral.
