The correct answer would be D
Gregory Stock is considered to be an expert in biotechnology. He has spent much of his career working to develop therapies for various conditions. He would be most qualified to write about new technologies in medicine.
The revision that would help expand the ideas in the excerpt
above would be adding more specifics about the sailors' beliefs about the
island.
To add, the Most Dangerous Game opens with a conversation
between two men—Whitney and
Rainsford.