Question

what material is strip mining mainly used to extract?
iron and copper
salt and limestone
gold and silver
coal

Explanation:

Strip mining is a surface mining method ideal for extracting minerals that lie close to the earth's surface in horizontal layers. Coal is the most common material extracted this way, as many coal deposits are shallow and extensive, making strip mining efficient for their recovery. The other listed materials are typically extracted via underground mining or other surface methods more suited to their deposit characteristics.

Answer:

coal