Concept:Lubricants reduce friction by creating a slippery layer between two surfaces in contact.Explanation:Grease is a semi-solid or highly viscous lubricant.It clings better to metal surfaces than kerosene, water, or petrol.Because grease remains between moving parts, it minimizes direct contact and therefore reduces friction more effectively.The other liquids are thin and quickly drain away, offering less lasting lubrication.Answer:B. grease