The fact that he found the blue carbuncle
D I believe. Seems to be the only relevant.
The meaning of this idiom is that you should never feel hopeless when times get hard or difficult because difficult times always lead to better days. The difficult times are like dark clouds that blocks the sun. When we look at the edges of the cloud more closely, we can see the sun shining there like a silver lining.
Grim melancholy would be the answer
Answer:
A: Antithesis: he is using contrasting ideas to emphasize the uncertainty of space exploration
Explanation:
Just a tip, look for the opposites, he's used antonyms to exaggerate his thoughts on the knowledge mankind had on space.
Hope this helps! :D