In greek you can say μου αρέσει να τρώω πορτοκάλι or πορτοκάλια, with no difference in meaning. In english you have to use the plural, though.
I feel fine with the English question, "Do you like eating orange?" However, it conveys something more akin to liking the process of eating oranges, rather than liking the taste of oranges themselves. Not sure how this distinction maps on to the Greek expression.
I got - you like eating oranges - marked wrong. But this could be a question, in English, depending on the intonation.
It would be helpful if you would explain what is incorrect about it -- and also what you meant with "the answer that is given", as you may have seen any of several accepted alternatives.