Concept:A trade association is a group formed by businesses in the same trade or industry to protect and promote their common interests.
Explanation:The most important role of a trade association is to encourage unity among its members.
It helps them cooperate on issues such as pricing, trade policies, and dispute resolution.
Fostering cooperation among members strengthens the trade and helps members achieve shared goals.
Option B, establishing a link among members, is only a minor aspect of this cooperation.
Options C and D are not core functions of a trade association.
Therefore, fostering cooperation among members is the major function.
Answer:A. foster cooperation among members