You are presented with the question "Plant reproduction often requires something that causes what?" and the following answer choices: 
- mutations
 - bloom time
 - An earthquake
 - Steam
 - seeds
 - The common cold
 - gene flow
 - Allergies

Now knowing that plant reproduction often requires pollen and hay fever or pollen allergy is the most prevalent allergy, choose the best answer.


 

        Allergies 