Concept:Within the Commonwealth of Nations, member countries exchange special diplomatic representatives called High Commissioners instead of Ambassadors.Explanation:Among Commonwealth members, the senior diplomat sent to another member nation holds the title of High Commissioner.The diplomatic mission itself is known as a High Commission rather than an Embassy.This unique practice distinguishes Commonwealth relations from diplomatic ties with non-Commonwealth countries, where the representative is called an Ambassador.Therefore, when one Commonwealth nation represents itself in another member nation, it appoints a High Commissioner.Answer:A. high commissioners