Which is a concluding sentence from the paragraphs of this passage?

A)
The poor water circulation inside most blue holes makes them anoxic.

B)
The Great Blue Hole is now one of the country’s top tourist attractions.

C)
The Great Blue Hole is the result of repeated collapses of an underwater cave system during the Ice Age.

D)
The Seven Natural Wonders of the World include incredible places like Mount Everest, the Grand Canyon, and the Great Barrier Reef.