Final answer:
The answer to the question is that Paul directed the Philippian believers to live out their citizenship in a manner worthy of the gospel of Christ, which means as citizens of heaven. This concept is rooted in the spread of Christianity and the cultural experience of the Greco-Roman world.
Step-by-step explanation:
Paul directed the Philippian believers to live out their citizenship in a manner worthy of the gospel of Christ, and so demonstrate that they were truly c) As citizens of heaven. In the spread of Christianity, Paul encountered the religious and cultural experience of the Greco-Roman world, which played a major role in the formation of Christianity. Romans valued citizenship, and being a citizen in the Roman Empire granted certain legal and political rights. However, Paul emphasized that the true citizenship of believers lies in heaven, and they should live according to the principles of the gospel of Christ.