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 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]: [header] How to get rid of the whitefly [title] Vacuum the flies. [step] Use a small hand vacuum, or hold the furniture-cleaning nozzle of a standard vacuum cleaner. Walk around your infested plants and suck the pests from the undersides of the leaves and foliage. <sep> (A) This method is quick and straightforward, and it can remove whiteflies from all stages of the development cycle-from larvae to mature, plant-munching adults. Vacuuming is most effective as soon as you notice an infestation. (B) [substeps] Lice/hornets that have infested the insect where possible will probably cause an infestation when they have access to this species. Lice and hornets can be pregnant bees or even cobwetters. (C) [substeps] Once you've vacuumed up all of the insects, you can dismantle the insect and wash it off. Plant diseases like freeze burn-gas are very likely to have mites, fungus, or other biological problems with this insect. (D) [substeps] If possible, clean the potted plants as a habit to keep the insects away. [title] Tear off the hard outer leaves once the insects have died.
[A]: A


[Q]: [header] How to stop howling dogs [title] Ignore your dog's howling. [step] Some dogs will howl in order to get your attention, or to " ask " for food, treats, toys, etc. To prevent this kind of howling behavior, you will first have to show your dog that howling is not a way to get your attention. <sep> (A) [substeps] Don't scold or punish your dog when it howls, as it may find even this kind of attention rewarding. Simply do not touch, speak, or look at your dog when it howls to get your attention. (B) Yelling back to your dog may just make him think that you are too busy to respond to his howling. Plus, yelling back won't give him any effect. (C) [substeps] Yelling or hitting your dog will only cause it to howl. Ignoring, however, is best done in conjunction with its howling behavior. (D) You will also have to stop and listen to your dog carefully as it is howling. [substeps] Make sure that you are between the dog and two people in a car or apartment building when your dog yelps.
[A]:
A