Fact 1: Fertilization occurs when sperm swim to an egg inside an archegonium.

Fact 2: Each archegonium contains a single egg that is embedded in the prothallus.

Given the two facts above, answer the question "What happens inside the single egg embedded inside the prothallus " with the following options: 
- Earth revolving around the sun
 - The area was once underwater
 - gastropod shells
 - it keeps an organism warm
 - remains of prehistoric life
 - fertilization occurs
 - allow growth
 - It helps them survive


 

      fertilization occurs   