Concept:A trade association is a group formed to protect and advance the common interests of businesses in the same industry.Explanation:Paying salaries to members is not a function of a trade association.Providing loans to members is not its primary role.Guaranteeing employment for members is also not its main purpose.A trade association mainly works to protect the interests and improve the general welfare of its members.Therefore, promoting members' welfare is the correct option.Answer:B. promote members' welfare