The correct answer is D. To expose the environmental threats posed by ridgetop development.
Step-by-step explanation:
The text presented explains the effects of ridgetop development, this includes the idea this type of development represent a threat for the mountains "One of the most serious threats to our mountains is ridgetop development" which is explained by the author as ridgetop development affect the scenic view and therefore the economy of the zone, besides this, the author explains ridgetop development has a direct effect on the environment because it causes erosion and has an effect on water sources. According to this, the main purpose or objective the author has with this text is to point out the thread or negative effects of ridgetop development or "to expose the environmental threats posed by ridgetop development".