The correct answer is option 3, the Ottawa Agreement. The policy of `imperial preferences` refers to the trade agreement that was reached at the Imperial Economic Conference held in Ottawa, Canada, in 1932. The agreement aimed to promote trade between Britain and its colonies by granting preferential tariffs on certain goods. This meant that the colonies would receive favorable treatment in terms of tariffs and trade barriers when trading with Britain, compared to other countries. The Ottawa Agreement was an important step in strengthening economic ties within the British Empire and increasing economic cooperation between Britain and its colonies. It helped to establish a framework for economic relations that would be expanded upon in future years.