"They see a cat."
Translation:Ils voient un chat.
Duolingo doesn't display the "play audio" button until at least one comment is posted. So I wrote that partly because I wanted to hear the pronunciation and also because I consistently write "voyent" when it should, as you correctly state, be "voient".
But I also suspect that's a fairly common error. So I also wrote what I wrote because I'm sure someone will see this and relate to my reaction and it could hopefully serve as a reminder to both them and I in the future.
There are quite a few examples of words that sound identical but have different meanings, just as there are in English. Often, the only way to tell them apart is the context. So if you're talking to someone about a group of people and you hear "Il voit", there's a good chance they're actually saying "Ils voient".