AGraphite
BDiamond
CCoal
DCharcoal
Answer:
A. Graphite
Read Explanation:
Graphite Properties
Graphite is an allotrope of carbon where each carbon atom is bonded to three other carbon atoms in a hexagonal array, forming flat, two-dimensional layers.
These layers are held together by weak van der Waals forces, which allow them to slide past one another easily. This sliding property makes graphite an excellent solid lubricant.
It is commonly used in machinery operating at high temperatures where traditional liquid or oil-based lubricants might decompose or burn off.
Graphite remains stable and retains its lubricating properties even under extreme thermal conditions.
Diamond: Unlike graphite, diamond has a rigid, three-dimensional tetrahedral structure held together by strong covalent bonds. It is the hardest known natural material and acts as an abrasive rather than a lubricant.
Fullerenes (C60): These are cage-like structures known as 'buckyballs.' They have distinct chemical and physical properties separate from both graphite and diamond.
Graphene: A single layer of graphite, just one atom thick. It is known for extraordinary tensile strength and electrical conductivity.