question! thank

answer答复;回应 这是最通用的词,对一个提问,任何言词,文字和动作上的回应,都可以叫answer.在很多情况下,常不涉及回复的具体内容.

I cannot answer you right now 我不能马上答复你
He answered her question with a wave of his hand 他挥了挥手,作为对她的问题的答复
He answered that he knew nothing about it 他回答说,他对此事一无所知
Please give a pormpt answer to my request 请对我的请求及时答复

respond回答,回(响)应 较正式的用词作为一种回答,常常是人们所期待的,或所热望的.

He failed to make any response to my request 他对我的请求未做任何回应
Please respond to the question 请对这个问题做出回答(应)
Our appeal for help met with no response 我们求助的呼吁没有得到回应
I invited her to dinner but she did not respond. 我请她吃晚饭，但她未作回答。
参考资料：汉英双解英语同义词词典

answer reply respond
均含有“回答”的意思。
answer 是常用词, 可指“口头”、“笔头”, 甚至“行动”回答, 如:
He answered my question.
他回答了我的问题。
reply 较answer正式, 如:
I sent in my application, and the university replied immediately.
我把申请书交上去了, 大学方面立即给了答复。
respond 系正式用语, 指“对号召[职责、请求等]作出自发性的适当反应”, 如:
They eagerly responded to the Party