You will be given a definition of a task first, then some input of the task.
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 improve your vision naturally [title] Find a pencil, and mark it somewhere in the middle. [step] Draw a letter, number or dot on the side of the pencil. For this exercise, you'll focus on the pencil and the dot as you move it toward and away from your eyes. <sep> (A) [title] To start, place the pencil vertically in front of you, and draw a circle around it to represent the pupil size. [step] Move the pencil as far away from your eyes as you can. (B) Work from left to right, not side to side. Move this pencil a few inches (comfortably) in each direction, but don't accidentally mark it. (C) Pencil push-ups are reputed to correct double vision and crossed eyes, but it can't hurt to try them for other issues-it's free, painless, and only involves focusing and refocusing your eyes. [title] Hold the pencil in front of your face, at arm's length. (D) [substeps] There are many color pencils you can use, but there are two main colors used: a black and white, a deep black and a deep tan. The colors of these pencils differ depending on the subject you're focused on.
Output:
C