"Kucing itu memakan ikan."
Terjemahan:The cat eats fish.
Kucing itu seharusnya that cat. The seharusnya digunakan untuk Sang atau si. Contoh : The Lion = Sang Singa atau Si Singa.
"That cat eats fish" should be accepted too.
Indonesian speakers do not use "sang" and "si" the way English speakers use "the". This makes it difficult to translate, which is why Duolingo uses "itu" in this sentence. Here is an example where "sang" and "si" fails badly: "They took the plate."