Assuming we're just looking at this phrase, "learn'd" suggests that the astronomer studied to become intelligent in the astronomical field.
Answer:
D
Explanation:
They charted the movements of the sun, moon and stars
Fire or Mass destruction should be the answer. I hope this helps! : )
Cushion or protection. It says that it keeps heating bills low in the winter. Meaning, they're blocking the cool air, and keeping the heat from escaping.