Primary succession is when things that grow on rocks and don't need soil, like lichen, break down the rocks and turn them into soil.  Then things that grow on soil can grow, like algae and fungus and firther break down the soil.
The successional stages would be larger organisms like plants and animals.  
        
             
        
        
        
<span>This study is a scientific study that links certain diseases with things that might causing them. Diabetes and heart disease are two of the most prolific ailments in modern humanity and this studies goal is to determine their cause and more importantly how to stop them.</span>
        
             
        
        
        
This should be an example of genetic drift.
The brown spotted deer would spread their genes more than the white spotted ones which would eventually lead to them completely overpowering genetically the white deer in future generations.
        
                    
             
        
        
        
Im pretty sure its c but hope this helps :)