You are presented with the question "what is individuals moving into or out of a population?" and the following answer choices: 
- Greenhouse gases
 - rapid expansion
 - Burning fuel and air
 - permineralization
 - peachleaf willow
 - competition
 - unidirectional
 - food and shelter

Now knowing that gene flow occurs when individuals move into or out of a population and gene flow between populations is unidirectional, choose the best answer.


 

       unidirectional  