Answer: D. high population densities
Explanation:
High population densities as noted in the excerpt, make coastal areas very prone to climate change conditions due to the environmental pressure exerted by such huge number of people.
The people in Indonesia will be more prone to climate change effects such as flooding as water levels rise and continue to encroach on the islands which no doubt have houses close to the coast due to the high population densities which means that a lot of people are in danger of losing their homes.