Definition: 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".
Input: [header] How to add color to gum paste [title] Select this procedure when you need small amounts of several different colors. [step] Gum paste will begin to harden if exposed to air. Keep unused portions in a sealable bag or air-tight container to retain moisture. <sep> (A) The mask will have to be adapted to your mouth rather than your teeth. [title] Open your mouth and brush your teeth and gums (or tongue) with the gum paste. (B) [title] Work with a little bit at a time. [step] After you take it from the container, the gum paste may be stiff. (C) [title] Open one remaining piece of gum paste, then add your color. [step] By rolling the paste between your fingers, you can extract the color from the rim of the container. (D) [substeps] Gum paste that is exposed to air can potentially harden, retaining some of its bright color and making it harder to reveal new color. This process will also clear any potential stains or bacteria that were created along with the paste.
Output:
B