The correct option is D In crucibles
Graphite is a crystalline allotrope of carbon.
It is slippery in touch and has a high melting point because of which it is used as a dry lubricant in machines that work at high temperatures. It is also used for building crucibles for melting metals.
It is mixed with clay and used in lead pencils as it can leave grey marks on paper.
It is brittle in nature and hence cannot be drawn into wires.