"The dog sees a fox."
Translation:Lišku vidí ten pes.
It seems to be a mistake. Active voice (činný rod) : "The subject" sees "an object" or another "subject". The dog sees a fox should be "Ten pes vidí lišku" Pasive voice (trpný rod): "object" or "another subject" has been seen by "the subject". The dog has been seen by a fox should be "Liška je viděna psem"
There is no mistake here. Do not complicate the stuff with the passive voice, it just does not belong here, both sentences are active.
The Czech word order is flexible and it does not change the main meaning, only the emphasis or comment/topic.
This is backwards. The sentence you're supposed to choose actually says that the fox sees a dog.