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".

[header] How to be useful and help contribute to society [title] The feeling of being useless can come from deep psychological mechanisms. [step] Simply being useful may not stop the feeling of being useless. In contrast, not contributing to society (leeching society's benefits) may create or amplify many negative feelings. <sep> (A) [title] The essence of human productivity is taking one kind of good and turning it into another kind. [step] In order to make some output, you need input. (B) Focus your attention on the positive aspects of society, such as upholding values, not manufacturing inequalities, or making a good living. People who are good at things actually make great economic tools. (C) If you find yourself feeling this way for no good reason, dissociate yourself and seek outside solutions of your own. [substeps] If you are feeling overwhelmed by disagreeing with others, delegate this task to a trusted trusted friend or colleague. (D) In contrast, a boss wouldn't feel he can be doing the job well. You could be contributing because your employer values quality over personality, and the responsibilities you assigned to you are superior.
A