Assuming we're just looking at this phrase, "learn'd" suggests that the astronomer studied to become intelligent in the astronomical field.
D is the most appropriate answer, so i would pick that one.
Charles. The day of her murder he was at Mrs. Huffington's house. Previously he had an affair with Mrs. Huffington, they were caught cheating Mr. Huffinton and Charles was fired and couldn't make a living because he only knew the business of cleaning pools.