You are presented with the quiz "Bottleneck effect can occur with " But you don't know the answer, so you turn to your teacher to ask for hints. He says that "bottleneck effect occurs when a population suddenly gets much smaller" and "population growth is reduced by external migration". So, what's the best answer to the question?
Available choices: a. external migration. b. direct damage to the lungs. c. Movement of an air mass. d. competition. e. if humans disturb bears. f. competing for resources. g. Plant growth is reduced. h. Temperature changing.
a.