Please choose the correct ending to complete the given sentence: Food and Entertaining: [header] How to make rainbow frosting [title] Beat the butter in a large bowl using an electric mixer. [step] Blend and cream well on a medium setting, mixing until the butter is fully whipped, taking about 2-3 minutes. [title] Pour in the powdered sugar.

Ending1: [step] Slowly blend in the powdered sugar on low speed. Blend until the frosting becomes stiff, taking about 2-4 minutes. Ending2: [step] For fluffy frosting, add the powdered sugar last. Mix thoroughly, then just throw it into the bowl. Ending3: [step] Beat again, until well-combined. [title] Blend all of the ingredients except the powdered sugar and vanilla to combine well, and then knead the mixture until fully incorporated. Ending4: [step] Continue mixing, adding the powdered sugar to the mixture gradually, being sure not to mix while beating. [title] Add the raisins to the mixture.

Answer format: ending1/ending2/ending3/ending4