Concept:A leavening agent releases gas to make cake batter rise.Explanation:Banana cake is a type of cake batter that needs a reliable chemical leavener.Baking powder is a complete leavening agent containing both an acid and a base, so it works well in cake preparation.Cream of tartar and bicarbonate of soda may need additional acidic ingredients, while palm wine is not the standard leavening agent for banana cake.Answer:Baking powder.