Me too. This is a listening exercise. Is there any possibility that each time we have to listen a letter, both the letter itself and the full name of the letter are accepted as the correct answer? 'Cuz such kind of problem is not just occurring for once only; it has occurred in quite some other listening exercises such as (for example) the "το γράμμα η" series.
Since we have included every possible combination and single version of each letter many should be accepted. So the problem is what the Duobot decides to choose. There is no way we can influence that mad machine but we are working on a new tree which should bypass these issues.
In the meantime, I suggest you get out of the ABC skill by any means you can --- do not do Strengthen skills for ABCs; it is problematic. I assure you the following skills are really much smoother.
Thanks for your patience. And good luck and happy learning. Any questions you have we will try our best to answer.
Since we moderators are unable to see any of the exercises done by learners, nor what the response from the program that grades the exercises said we have no way of knowing what the problem might be. You should report this on the page selecting: My answer should be accepted, and /or send a screenshot.
Did you try the answer at the top of this page? "theeta and throne" if that was also rejected please send a screenshot so we can rule out a technical error. Also, one of these should be accepted: "[th/thita/theta/t] and throne"
Since we are unable to see what you wrote, nor what the exercise was nor what Duo's reply was we can't help without the sscreenshot.