Part A
The phrase "a born Arctic explorer" suggests that Hall had a lifelong interest and natural ability in Arctic exploration. Therefore, the correct answer is:
3. He had a lifelong interest and natural ability in Arctic exploration.
Part B
The detail from the passage that best supports the correct answer from Part A is:
4. "he held fast to one fancy."
This detail indicates that Hall had a consistent passion for Arctic exploration, aligning with the idea of a "born Arctic explorer."