Q: In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".
[header] How to make thumbprint cookies [title] Place the butter, sugar and vanilla extract in a large mixing bowl. [step] Beat the ingredients together with a handheld mixer or a stand mixer with a paddle attachment, mixing on medium speed for about 2 minutes. [title] Pour the flour and salt into a sifter or a sieve. <sep> (A) [step] Ensure that you do not spill the flour as you add it. If there are any solids in the mixture, gently shake them out. (B) [step] How much you add will depend on how thick your dough is. If it is hard, or you want extremely thick cookies, add just a tiny bit. (C) [step] Do not have an electric mixer, as these will do the job. [title] Add the oil, if you don't have one. (D) [step] Either crank the sifter over a second mixing bowl or tap the sieve so that the flour and salt sift through the mesh and into the bowl. [title] Add 1 cup of the sifted dry ingredients into the butter mixer, mixing on low speed until just combined.
A:
D