An author who wanted to develop their narrator as a character might make use a narrative style

The correct answer is close.
If an author uses a close narrative style, it means that he or she is paying special attention to the characters they want to develop and bring closer to the readers/audience. If the character is unreliable, or reliable, or distant, that's not going to help the audience much to understand the character in-depth. That's why authors opt for a close narrative style instead.