Need help ASAP! Which best expresses the main idea of this passage?

A) Scuba-diving is an extremely expensive and challenging hobby, but it also has many rewards.

B) In 1972, famed explorer Jacques Cousteau took his one-man submarine into the depths of the Great Blue Hole.
C) The Seven Natural Wonders of the World include incredible places like Mount Everest, the Grand Canyon, and the Great Barrier Reef.
D) The Great Blue Hole off the coast of Belize is one of the most wondrous and scientifically interesting natural wonders