Fact 1: Plant reproduction often requires pollen.

Fact 2: Hay fever or pollen allergy is the most prevalent allergy.

Given the two facts above, answer the question "What is required for plant reproduction?" with the following options: 
- By wind and rain
 - Something that is found on a cloud
 - fertilization occurs
 - Males and females
 - Something that comes from a volcano
 - Something that is invisible
 - Something that causes allergies
 - sperm and egg fuse


 

       Something that causes allergies  