To answer questions, you have a few options.
是 or 是的 can be used to answer when something "is".
例句：你是Mark嗎？是。Are you Mark? Yes (I am).
例句：你是烏克蘭人嗎？Are you Ukrainian? 是的。Yes (I am)
對 is used to answer a question when the speaker is expecting the answer to be a certain something. The best translation is "that's right" or "right". Basically, when somebody is asking whether something is correct or not
例句：你喜歡看書，是吧？對啊！You like reading books, don't you? Yeah!
例句：咱們這兒拐彎兒，對吧？對。We turn here, right? Yeah.
例句：你下個星期要去威爾士嗎？對。Are you going to Wales next week? Yeah, that's right.
Be careful with one right though, this is where English and Chinese differ.
你不是老師嗎？You aren't a teacher? 對 That's correct.
In English we'd say "no" here, but in Chinese you are confirming what they said is correct.
你不喜歡喝茶嗎？You don't like drinking tea, do you? 對 That's right, I don't like tea
You can say 沒錯（兒）meaning "that's right" (literally "not wrong"). (This is quite a strong answer)
例句：你姓張媽？沒錯！Is your surname 張？That's right!
行 can be used for "OK" or "alright"
例句：你今晚想看電影兒嗎？行。Do you want to watch a movie tonight? Yeah, alright
可以 Can be used for "yeah, alright" or "OK" or "can/could do" in much the same way as 行
例句：你今晚想看電影兒嗎？可以。Do you want to watch a movie tonight? Yeah, alright
好的 is "OK" in a positive sense
例句：你現在想喫贊飯嗎？好的。Do you want to eat breakfast now? Yeah, OK.
When you are being asked a question with a verb in it, you reply like this:
你喜歡喝咖啡嗎？喜歡？Do you like coffee? Yeah, (I like it).
It can also mean "to"
例句：我對小貓兒過敏 I am allergic to cats
例句：我對他説 I say to him
例句：我對中華人民共和國共產黨的歷史很感興趣 I am very interested in history the history of the Communist Party
例句：我對北京不太熟悉 I'm not that familiar with Beijing.