Based on what happens to Citizen X, under which government does he live?

The correct answer is C) Rome, because Roman law forces the accuser to have a burden of proof.

Based on what happens to Citizen X, he lives under the government of Rome.

When we are talking about the term Burden of Proof it means the accuser has to prove his claims. So, in simpler terms, it's the obligation of the accuser to present the elements that support his claim. In the case of the example, Citizen X lives in Rome because he has to present the proofs that his co-worker stole the watch. There were no proofs, then, the co-worker was found not-guilty in the absence of proofs.