Sagitta, This may be incorrect for a translation because in my knowledge of Anglophones, if it were a singular sport the name of the sport would be used. However, at this stage of learning your language it might be more important to help the student understand via reinforcement and consistency the differentiation between singular and plural. There is one variant of exercises that is titled "Write this in English", so "sport" should be correct because it is the same case and tense. The idea is conveyed despite the linguistic awkwardness. спорти as compared to спорт in this sentence would likely cause the same response from native Ukrainian speakers simply because that is NOT how it would be said. Is it the goal of DuoLingo that students learn the concepts of the language or the minutia of idiosyncrasies of the different language structures?