What conversion takes place in a motor? O A. An electric current into a magnetic field
B. A lower voltage into a higher voltage
O C. Mechanical energy into electric energy
O D. Electric energy into mechanical energy

I think the answer would be C

Ancient civilizations had a high demand for raw materials, like clay, diverse rocks and, most of all, metals. These were required for buildings, crafts, agriculture, their armed forces, financial concerns, art and culture. Clays and rocks produced by opencast mining primarily served for the production of bricks and building blocks, which were used for civil and hydraulic engineering.