The correct option is C When wood is burnt in a limited supply of oxygen and water until volatile materials are removed, the residue is charcoal.
When wood is burnt in a limited supply of oxygen until water and other volatile substances are removed, the remaining residue is called as charcoal. It is lightweight carbon and ash. The two most common types of charcoal are common charcoal and activated charcoal. Common charcoal is produced from wood, peat, coal, coconut shell or petroleum. Activated charcoal is porous charcoal, capable of absorbing impurities and it is made for special medical uses.