One one side of the Punnet Square, label B. The other, Label b. Take the upper right corner for example. The solution would be Bb. 
        
             
        
        
        
C human selection is the answer hope this helps 
        
             
        
        
        
a)121 million gigatons or 121 million billion metric tons" of carbon).
B)The ocean, with around 38,000 gigatons
c)60 gigatons of carbon
 
        
             
        
        
        
The role of mass extinction in evolution. At the most basic level, mass extinctions reduce diversity by killing off specific lineages, and with them, any descendant species they might have given rise to. ... But mass extinction can also play a creative role in evolution, stimulating the growth of other branches.