Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Ha Long Bay, (19) _______ is located in Quang Ninh Province, is one of the most famous natural wonders of Vietnam and the world. It was recognized as a UNESCO World Heritage Site for its breathtaking beauty and geological value. The bay covers a large area with nearly two thousand limestone islands rising from the emerald water. Each island has its own (20) ________ shape, such as the Dog Island or the Fighting Cock Islet.

Visitors can take a cruise to admire the scenery, (21) _______ mysterious caves, and swim in the crystal-clear sea. Some people also love (22) _______ to get closer to nature. At sunset, the view of the golden light reflecting on the calm water is truly unforgettable.

Ha Long Bay is not only a symbol of Vietnam's natural beauty but also a reminder of how important it is to protect our (23) ________ for future generations.