The Parable of the Persistent Widow (Luke 18:1-8) is primarily intended to illustrate what specific theological principle regarding prayer?

A The importance of praying at specific times and in specific locations to be heard by God. B The necessity of offering extravagant gifts and sacrifices to persuade God to answer prayers. C The value of unwavering persistence and faith in prayer, even when answers are delayed or seem impossible. D The idea that God only answers the prayers of those who are righteous and morally blameless.