Write the next sentence in the following story.

How to make root beer float cookies
Preheat the oven to 350 f (180 c).
Line 2 baking sheets with parchment paper.
Place the butter, granulated sugar and brown sugar in a mixing bowl.

[A]. Pour in the dry ingredients and whisk until evenly combined. Add the vanilla and cream and whisk the dry ingredients until well-combined..
[B]. Mix until the ingredients are fully combined. Blend in the sugar gradually as it is mixing in until fully incorporated..
[C]. Beat them together on low speed using an electric mixer. Scrape them on the counter to help grind them up more thoroughly..
[D]. Beat the ingredients at medium speed with a handheld mixer or a stand mixer with a paddle attachment. When you're done, the butter mixture should be light and fluffy... The answer should be
[D].