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". 

[EX Q]: [header] How to polish rocks [title] Choose the right rock. [step] You can polish any stone you wish, but there are certain characteristics of a stone that will make it easier to polish. If you want an easy stone to polish, pick a somewhat softer stone like onyx, limestone or calcite. <sep> (A) [substeps] You can polish diamond, granite or ceramic stones by cutting thin pipe holes or inserting dry mortar into one side of each hole. Look for a stone that resembles a diamond, but not necessarily a diamond. (B) Otherwise, a smoother, more pumice-like stone will be more difficult to polish. [substeps] Emeralds and equilateral manganese are both excellent mineral polishes. (C) Stones that are very hard will take a much longer time to polish. However, though hard rocks take a long time to sand, they yield more shine than softer rocks. (D) Softer rocks will actually work more well, and might look better to polish very old stones, but brighter stones tend to chip quicker. [substeps] Rubies, sapphires, and emerald are good options.
[EX A]: C

[EX Q]: [header] How to whitewash trim [title] Set up your working area. [step] Cover the floor with a drop cloth to keep dust and whitewash off of it. Open screened windows and doors to provide ventilation. <sep> (A) Keep the temperature low to avoid fumes and keep your work area clean. Additionally, have at least one sheet of newspaper in case a lightning storm or other electrical emergency strikes strikes your home. (B) Set all of your supplies in a corner of the room so you know where everything is. [substeps] If you don't have a lot of experience painting, use painter's tape to tape off areas you don't want to get whitewash, like the walls. (C) [title] Consider using a small piece of velcro, preferably one in a similar color, to lock in moisture in the paneling. [step] For smaller boards, make sure to allow at least 24 hours for the patch to dry between applications. (D) You may also want to swing curtains over them for a soft and light cleaning that will come before whitewashing. There are online projects to do, or you can perform laser removal yourself.
[EX A]: B

[EX Q]: First the man introduces himself and what he does. Then he shows us how he paints a picture of nature. next he <sep> (A) shows us a wheel in the tire of his car. (B) takes items off the table next to him in front of several brushes and paints them. (C) puts stickers on the tree to finish the stuff. (D) gives an introduction to materials and an understanding of pigments and he talks in between his lessons.
[EX A]:
D