Answer:
C. A concentration gradient must exist.
 
        
                    
             
        
        
        
Answer:
Atmosphere
Explanation:
carbon dioxide is naturally released into the atmosphere by the decay and flatulance of animals. But you extract fossil fuels from the ground and burn them. The burning of fossil fuels is called combustion. 
 
        
             
        
        
        
B parasitism 
a parasite feeds off another organism therefore helping itself but hurting the other organism 
        
                    
             
        
        
        
Answer:
Unsaturated fast is a type of fat containing a high proportion of fatty acid molecules with at least one double bond, considered to be healthier in the diet than saturated fat. And Saturated fat is a type of fat containing fatty acid chains that have only single bonds, and considered not healthy if consumed much of
Explanation:
 
        
             
        
        
        
Point Mutation !! It is a mutation affecting only one or very few nucleotides in a gene sequence.