ANS:C - Iron ore

Limestone is not a charge material for cupola. A cupola furnace is a type of melting furnace used in foundries to melt cast iron. It operates by melting metal and producing a controlled amount of slag. The charge materials for a cupola typically include:

1. Iron scrap: Scrap metal, such as old machinery parts, automotive components, or other iron-based scrap materials, is commonly used as a feedstock for melting in the cupola.
2. Iron ore: Iron ore may be added to the charge to provide additional iron content and adjust the chemistry of the melt. However, in cupola melting, iron ore is not typically added directly to the furnace, as the primary purpose is to recycle existing iron scrap.
3. Pig iron: Pig iron, a form of crude iron produced by smelting iron ore in a blast furnace, is often added to the cupola charge to supplement the iron content and provide additional heat during melting.

Limestone, on the other hand, is not a typical charge material for cupola furnaces. Limestone is primarily used in blast furnaces during the production of pig iron to help remove impurities and produce slag. In a cupola furnace, the focus is on melting scrap iron rather than refining iron ore, so limestone is not necessary for the process.