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

The Amazon Rainforest, a vast tropical rainforest located in South America, (17) ___________. It is home to an incredible variety of plant and animal species, many of which are still undiscovered. The forest is essential in regulating the Earth's climate and supporting biodiversity. Visitors to the Amazon can explore its unique ecosystem through guided tours.
The Amazon Rainforest is known for its rich biodiversity (18) ___________. This vast natural area also plays a crucial role in the global climate system, producing 20% of the world's oxygen. It is a vital part of our planet's health and survival.
Many tourists visit the Amazon to experience its unique wildlife and lush landscapes. (19) ___________. Additionally, indigenous communities living in the forest contribute to maintaining its ecological balance. Conservation efforts are crucial to protect the forest from deforestation and environmental threats.
Visited by thousands of eco-tourists every year, (20) ___________. Its significance in global environmental health has prompted many international organizations to support its preservation. (21) ___________. Efforts to promote sustainable tourism in the Amazon are helping to raise awareness about the importance of protecting this vital natural resource for future generations.

Mark the letter A, B, C, or D on your answer sheet to indicate the option that best fits blank (19) in the Amazon Rainforest passage.