In the Parable of the Unjust Steward (Luke 16:1-13), what theological point is Jesus primarily making about the use of 'worldly wealth' (Greek: 'mammon') by his followers?

A That accumulating wealth is inherently evil and should be avoided by all believers. B That believers should focus solely on spiritual matters and disregard material possessions. C That believers should use their resources shrewdly and strategically to advance God's kingdom and secure their eternal future. D That believers should give all their wealth to the poor immediately to demonstrate their faith.