Question

The Amazon Rainforest is one of the most important ecosystems in the world. However, it is slowly being destroyed. Areas of the rainforest are being cleared for farms and roads, and much of the wood is also being harvested and sold. There are several compelling reasons to protect this area. First, a significant number of pharmaceuticals are made from plants that have been discovered in the rainforest, and it's quite possible there are still important plants that have not yet been discovered. Secondly, the rainforest provides a significant portion of the world's oxygen and also absorbs great amounts of carbon dioxide. Without rainforests, global warming could accelerate. 
The main purpose of the passage is

 to explain why the Amazon Rainforest should be protected.
 to discuss how the rainforest has helped in the development of medications.
 to present the major reasons why the Amazon Rainforest is being destroyed.
 to argue that rainforest destruction is a major cause of global warming.

Answer 1

I think it is the first answer choice " to explain why the Amazon Rainforest should be protected." Because that's what the passage is about. Someone explaining why the Rainforest should be protected and what will happen if it is destroyed.