Correct Answer - Option 4 : Grease
Explanation:
A lubricant is a substance, which reduces friction between mating parts. Lubricants are grouped in three categories.
1. Liquid lubricants:
Some of the most commonly used liquid lubricants are mineral oil, fatty or vegetable oils, synthetic oils.
2. Semi-liquid lubricants:
Greases are most commonly used lubricants with a higher viscosity than oils. These are employed for slow speed and heavy pressure operations like drawing, rolling and extrusion processes.
3. Solid lubricants:
Graphite is the commonly used solid lubricant. Other types of solid lubricants are soapstone, talc, French chalk etc.
