Explanation:

The New Caledonian Barrier Reef is the longest continuous barrier reef in the world and the third largest reef as well. It is located in the New Caledonia in the South Pacific. Hence option 2nd is correct.

The New Caledonian barrier reef is located in New Caledonia in the South Pacific, and is the longest continuous barrier reef in the world and the third largest after the Great Barrier Reef of Australia and the Mesoamerican Barrier Reef.