"A bear is cooking a rabbit."
Translation:곰이 토끼를 요리합니다.
"곰이 토끼를 요리하고 있습니디" should be accepted. I think this is much closer to the original English sentence.
But as you know, English uses the present continuous much more than other languages. Your Korean suggestion has practically the same meaning in this case. It should be accepted though, you're right, just not in place of the one there.
No criticism of you, but the audience here is new Korean learners. They cannot be expected to know a priori about the frequency of use of progressive tense in Korean. When Duo provides a prompt in English, it should accept (as correct) a direct translation. Here they prompted with English progressive, and they should have seeded the correct answers with the equivalent Korean progressive tense. If they want to accept present -fine. But it is both confusing and demoralizing for the student to be told an obviously correct answer is incorrect.
Thanks for the clear explanation. As you pointed out, the present continuous often appears in English, but not so frequent in other language. I understand "곰이 토끼를 요리하고 있습니디" is to be accepted as well. 감사합니다/ありがとうございます