Given the task definition and input, reply with output. 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".

There's an artist painting a square canvas board with several acrylic colors using a flat brush in a studio. she <sep> (A) is painting a christmas tree with a piece of acrylic text. (B) moves the brush across the screen several times. (C) shows how to cut the paint with the flat brush when time stops. (D) begins by painting blue strokes with the flat brush on the canvas surface.
D