Final answer:
When a person is sanctified, Christ's righteousness is applied to the believer. This means that the answer to fill in the blank is 'b) Applied.' Justification involves a legal declaration of righteousness, while sanctification is the ongoing process of becoming more holy, during which Christ's righteousness continues to be applied.
Step-by-step explanation:
When a person is justified, Christ's righteousness is imputed to the new believer. When the same person is sanctified, Christ's righteousness is applied to the believer. Therefore, the correct answer to fill in the blank is 'b) Applied.' To explain further, justification can be seen as a legal declaration where God pardons the sinner and accepts them as righteous, on the account of Christ's righteousness. Sanctification involves the actual process of being made more holy, and it is during this ongoing process that Christ's righteousness is applied to the believer, helping them grow in personal holiness and moral living.