You are presented with the question "Severe droughts may cause " and the following answer choices: 
- evolution
 - population growth
 - forest is destroyed
 - species variation
 - major threat to health
 - Dehydration
 - the ground shaking
 - a bottleneck effect

Now knowing that bottleneck effect occurs when a population suddenly gets much smaller and severe droughts have caused much of the rural population to urbanize, choose the best answer.


 

        a bottleneck effect 