Which best states the central claim in the passage?

Responses
A Professor Williams grew up in coal-mining country.Professor Williams grew up in coal-mining country.
B The coal mines still have some of the machines used to mine coal long ago.The coal mines still have some of the machines used to mine coal long ago.
C "Coal oil" lamps were the most importance piece of equipment for miners when they were at work deep under the ground."Coal oil" lamps were the most importance piece of equipment for miners when they were at work deep under the ground.
D Professor Williams originally intended to write about the mines of his hometown, but he became more fascinated by the lives of the actual miners.

D Professor Williams originally intended to write about the mines of his hometown, but he became more fascinated by the lives of the actual miners.