Final answer:
The mood expressed by CASCA is fear because the storm dropping fire is one of the worst he has ever experienced, indicating that the right answer is option B.
Step-by-step explanation:
The mood expressed in the excerpt from CASCA is best described as tense and in fear of the storm due to its unprecedented severity. Casca has experienced many storms, but this one dropping fire is unlike any other, suggesting either a 'civil strife in heaven', or the anger of the gods towards a world too arrogant. The mood is not excited, calm, or merely tense - it is underscored by a deep unease and trepidation towards the unusual and terrifying tempest, indicating the correct answer is B. Afraid of this storm because it is one of the worst of all he has experienced.