Concept:The consumer price index (CPI) is a measure of price changes for a specific group of consumers.Explanation:The CPI is based on the spending patterns of a particular population segment, such as urban households or industrial workers.It is not constructed for all people because it excludes rural or non-household groups.It is also not limited only to factory workers; other specific groups are also used.Thus, it is designed for a well-defined section of people.Answer:A. a well defined section of people