Fact 1: Mutations are essential for evolution to occur.

Fact 2: Evolution can be defined as continual progress.

Given the two facts above, answer the question "What is mutation essential for?" with the following options: 
- rapid expansion
 - sickness
 - a continual progress
 - resistance
 - growth
 - allow growth
 - Plant reproduction
 - chromosomes


 

   a continual progress      