The right answer is Lichen.
In ecology, a pioneer species is one of the first forms of life that colonize or recolonize a given ecological area.
Lichens are composite organisms resulting from a symbiosis between at least one heterotrophic fungus called mycobionte, representing 90% of all, and microscopic cells with chlorophyll (green algae or cyanobacteria autotrophic for carbon) called "photobionts" .
 
        
                    
             
        
        
        
Answer:
Hypothesis
Explanation:
A hypothesis is an educated guess, based on evidence provided by the initial question the scientist had. I hope I helped you:)
 
        
                    
             
        
        
        
The sun gets closer to the earth