Correct Option: A

Social cost is defined as a sum of the private cost and external costs. The social cost is generally not borne by an individual. It may be borne by entire society, city or even country. This is not a one-time cost like private cost. This cost is recurrent and it is very difficult to calculate due to the inclusion of external costs. The cost may result from an event, action, or policy changes. Social costs are not calculated whenever a seller sells any product or item to buyer. This cost is added up from the use of that product.