回复 一般用于文字交流的时候，例如回复短信(reply to a text message)，回复邮件(reply to an email). 回答 回答问题。answer the question. 答案 是一个名词，问题的答案(the answer to the question) 回应 比较接近respond. 用某个动作回应某人。act or behave in reaction to someone or something. 答复和回复差不多，答复更加正式一点。

回复：it's usually used to make a feedback for something related to yourself. As a noun: 你的回复我已经收到。 As a verb: 请你尽快回复我在邮件中提到的问题。 回答：when you reply to a question, it may be unrelated to you. As a noun: 你的回答对他没有任何帮助。 As a verb: 你能回答这个问题吗？ 答案：this is easier, it just be a noun. Not only a answer, but also a correct answer. As a noun: 我想得到一个最好的答案。 各位观众，答案即将揭晓。 Edited by Bruce Wechat:leisureleo, Skype: live:39252832 🐈🐈

非常好，回复和答复都可以使用。使用时没有那么严格。

谢谢 Bean！

First "答案” this word is noun ,not use in verb. 请在卷纸的空白处写上你的答案= Please write your answer in blank of paper. 回复 and 回答 ,noun or verb form both are ok.