In the Parable of the Persistent Widow (Luke 18:1-8), what is the primary theological point Jesus aims to convey about prayer?

A That God is reluctant to answer prayer and needs to be worn down by persistence. B That persistence in prayer demonstrates a lack of faith in God's timing. C That believers should always pray and not give up, trusting in God's justice even when it seems delayed. D That only widows and the vulnerable should be persistent in their prayers.