"Fish"

Translation: Ryby

[olaknowsbest]

Fish in English has an irregular plural. One fish. Many fish. It can be either just one, or several of the aquatic creatures, making this question just a matter of guessing.

[Vengir]

Duolingo should accept both singular and plural answer to this question. If it doesn't, report it.

[v.ivanov]

That'd be most easy phrase in a „Polish for Russian speakers“ course [that doesn't exist here yet]