Final answer:
d) Solemn. The speaker in the story is described as 'solemn'.
Step-by-step explanation:
In the story, the word 'solemn' BEST describes the speaker. The term 'solemn' means serious, grave, or somber. This suggests that the speaker is not cheerful or lighthearted, but rather has a serious demeanor or tone. The choice of this word may indicate that the speaker is discussing a serious or important topic in the story.