Italian also has a way of saying "really" to mean that: «Davvero?», used especially when you a friend tells you something incredible.
On the other hand, «È vero?» is used differently. It would be used for when, let's say, your child gets in trouble. A teacher reports to you what happened, so you turn to your child and say «È vero?». You would not say «Davvero?», which is used for casual conversations, just like "Really?"
I agree that a reply to something new, or surprising could very well be: "really?" in AE but the purpose of the lessons is to teach specific vocabulary and syntax. Otherwise, a whole host of replies might be possible: "Wow, I can hardly believe it!" "You don't say." "Wow, first time I've heard that." etc. That's why Duo has a rather narrow set of accepted replies.
@igfs Errors need to be reported on the exercise page using the "Report a problem" option or using "Support" on the left of every page. On this thread you are exchanging comments with other learners who have no power to make any changes. Check out this site: http://duolingo.wikia.com/wiki/Duolingo_Wiki#Getting_Help
If you are asking if something is "right" as in the right thing to do, that would be «È certo?». If you are asking if someone is right (and the other person is wrong) if two people are arguing, that would be «Ha ragione?». If something is "right," that does not necessarily have anything to do with truth. If the parents get out of work late but the grandparents are home, the right thing to do would be for them to get dinner started so that, when the parents come, they can all eat together. If the grandparents do not want to do it, they can say, "We can wait for you to get home and help you with dinner then." The parents might say, "You are at home already. If you make dinner, that would be one less thing we have to do when we get home from a tiring day at work." Both of them have not lied; both opinions are true, but the parents are right that the right thing to do would be for the grandparents to cook dinner.