The tiger caught a fox.

1. A fox has been caught by the tiger
2. A fox was caught by the tiger
3. A fox is caught by the tiger
4. A fox had been caught by the tiger
5. None of the above

Given sentence is in Past simple tense and it is inactive voice, we need to change it into passive voice.

Rule :
Subject + (was / were) + V3 + Optional Agents.