Answer:
The correct option is C.
Explanation:
Population bottleneck can be described as a wide reduction in the species of a population due to environmental factors or human activities. In the above scenario, population bottleneck occurred in the Northern elephant seals due to which their population reduced to just 20.
When a population of 30,000 was raised from just those 20 elephants, genetic drift occurred due to lack of variety. This caused the genetic diversity to reduce even in the population of 30,000.