Concept:A cooperative society is a member-owned organisation where members combine their resources for their common welfare.Explanation:The primary aim of a cooperative society is mutual benefit rather than profit.Members voluntarily pool their money, labour, or other resources to serve a common need.All members share the advantages of these pooled resources, and control lies with the members.Therefore, the form of business organisation where resources are pooled mainly for members' mutual benefit is a cooperative society.Answer:A. cooperative society