You are presented with the question "Bottleneck effect can occur with " and the following answer choices: 
- external migration
 - direct damage to the lungs
 - Movement of an air mass
 - competition
 - if humans disturb bears
 - competing for resources
 - Plant growth is reduced
 - Temperature changing

Now knowing that bottleneck effect occurs when a population suddenly gets much smaller and population growth is reduced by external migration, choose the best answer.


 

 external migration        