Answer:
A. The reader learns that she is confident and composed which makes her appear credible.
Step-by-step explanation:
Saki's short story "The Open Window" is about a character named Framton Nuttel who had gone to his new neighbor's house to be introduced. And while waiting for the lady of the house, he was told a rather ghastly story by the niece Vera, which was in fact, just a lie.
Through her narration of how her aunt keeps the window open in anticipation of the arrival of her husband and brothers from their hunting, Vera managed to 'horrify' Framton. So, when the hunting party arrived, Framton dashed out of the house, which Mrs. Sappleton admits "One would think he had seen a ghost". And Vera's declaration of how it must have been the spaniel that led Mr. Framton rushing out of the house shows how self-possessed she is and also contributes to the reader's understanding of her character. She finds joy in the scene and seems to be enjoying it. And her confident and composed nature at the scene shows her self-possessed nature.
Thus, the correct answer is option A.