The best answer to the question of why few people live in Serbia is A: the long distance between cities created isolation. This factor can contribute to a lower population density as it may limit access to services, jobs, and social opportunities, making it less attractive for settlement.
The other options, while they may present challenges in other contexts, do not accurately reflect the reasons for low population density in Serbia:
- B: Permafrost is not a significant issue in Serbia, which has a temperate climate.
- C: Serbia does not have several active volcanoes or frequent earthquakes that would discourage settlement.
- D: There are no widespread areas in Serbia that are off-limits for settlement for natural resource protection reasons.
Therefore, option A is the most appropriate choice.