Environmentalist: Many people prefer to live in regions of natural beauty.
Conclusion (Thus)
Governmentally mandated environmental protection in regions of natural beauty can help those regions' economies overall, even if such protection harms some older local industries.
Evidence
Many people want to live in regions with natural beauty. Such regions often get an influx of new residents, and as the population grows it encourages businesses to relocate to those regions.
Evaluate
There is a New Term in the conclusion: governmentally mandated environmental protection. We're drawing a conclusion about this thing, even though the author's argument didn't tell us anything about this thing, other than that it might harm some older local industries (which would weaken the author's conclusion).
So it's a very high percentage bet that the correct answer will refer to this. The author seems to be assuming that without the mandated environmental protection, the natural beauty would be spoiled in some way that would fail to encourage as many new residents and businesses to move in.
And it's assuming that with the mandated protection in place, the natural beauty is better preserved, and thus that new residents and businesses move in, which overall is a net gain for the region's economy.
Goal
Look for an answer affirming the author's internal logic (the mandated protection helps to preserve the natural beauty, which then acts as a magnet for more residents and businesses, which then helps the local economy overall).
Or look for an answer ruling out an objection (like mandated protection does not raise local taxes and prohibit activities in ways that have a net negative effect on the economy).