Paul taught that justification can only be obtained by

This question is testing your knowledge of Paul's teachings on justification. The question is asking which of the four options is the way to obtain justification according to Paul's teachings.

Justification means being made right with God, and Paul taught that justification can only be obtained through faith in Jesus Christ. This means that having faith in Jesus is the correct answer (Option C).

It's important to note that Paul also taught about the law of Moses, but he believed that following the law alone could not bring justification. The law was given to show people their sin and their need for a savior, who is Jesus Christ. Therefore, obeying the law of Moses alone is not enough to obtain justification (Option A).

Working hard on earth and going to church regularly are also not ways to obtain justification. These are good things to do, but they do not bring justification. Only faith in Jesus can bring justification (Option C).

In summary, the correct answer to this question is Option C: having faith in Jesus. To learn more about this, please read the relevant sections of the recommended textbooks.