Fact 1: Roundworms reproduce sexually.

Fact 2: Fertilisation is a key feature of sexual reproduction.

Given the two facts above, answer the question "What has to happen for roundworms to reproduce?" with the following options: 
- Fertilization
 - rapid expansion
 - Plants growth
 - an organism's body
 - permineralization
 - bioaerosols
 - temperature changes
 - competition


 

 Fertilization        