Which type of mining would NOT be used to mine coal

Coal is mined in two different ways: from deep underground and in

strip mines. In both cases the land that is mined is leased by the coal companies, while the ownership remains in public hands. Deep mines are reached through a shaft into the ground, through which miners gain access to the coal seam and out of which comes the coal. Strip mines are used when the coal seam is near the surface. The topsoil and other overburden materials are removed by giant power shovels and piled out of the way. The shovels then dig out the coal. After the coal has been mined, there may be environmental reclamation to return the land to its original state, thus allowing others continued use of it for their own purposes. This involves refilling the hole, spreading topsoil, and then planting new vegetation on it.

looks like the answer is     c     to me!