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". 

[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.
[A]: C


[Q]: [header] How to use psychology to close more sales [title] Give something for free. [step] The principle of reciprocation is a psychological phenomenon described by dr. robert cialdini, an expert in persuasion. According to this theory, it is part of human nature to feel obligated to repay debts of all kinds, big and small. <sep> (A) To begin this process, ask yourself if you really are willing to sell something for free. If you are willing to throw in the money, then you are probably willing to take credit. (B) You can't force anything on someone else. [substeps] If you " feel " obligation to a friend or loved one, give them something to ask you " if i use this method, what will happen? " [title] Assemble your argument. (C) If someone receives something free, they will feel a psychological urge to purchase a product to pay you back for your kindness. [substeps] Offer a free trial period, a sample, or even a pleasant experience. (D) To do this you must pay for or at least accept the full offer. After that you must devise a plan of compensation.
[A]: C


[Q]: A person is sitting on a dirt bike outdoors. the person <sep> (A) then gets up and becomes visible. (B) races and jumps the dirt bike across numerous outdoor terrains. (C) is playing a drum set. (D) is using a sprayer to clean dirt from the dirt bike.
[A]:
B