In the provided scene from "The Man Without a Country," the playwright develops the mood in a way that suggests a sense of calmness initially, as Nolan approaches the officers and engages in what he perceives as a pleasant conversation about reading. However, the underlying tension of Nolan's situation—his enforced isolation and the denial of news from his homeland—can create a sorrowful atmosphere as the scene progresses.
Therefore, the most fitting response based on the described mood development would be:
The mood is calm in the beginning of the scene, but as the scene goes on the mood becomes sorrowful.