In the Parable of the Persistent Widow (Luke 18:1-8), what primary theological point is Jesus making about prayer, beyond simply encouraging perseverance?

A God is obligated to answer prayers that are repeated frequently. B God's justice is contingent on the persistence of the petitioner, implying a transactional relationship. C God, unlike the unjust judge, is inherently just and will deliver justice to His elect, even though the timing may not align with our immediate desires. D The parable primarily emphasizes the importance of publicly demonstrating one's faith through constant prayer.