One of the major elements of natural selection is that all species have genetic variation. Natural selection is a process when organisms adapt better to their environment. It is an essential key in evolution. There is a change in phenotype of a population over time.
        
                    
             
        
        
        
Answer:
c) allowing an organism to adjust to changes in environmental conditions
Explanation:
A stimulus can be defined as any change in the external or internal environment that produces a corresponding response in the organism. These responses enable the organism to maintain an internal equilibrium (homeostasis). Gene expression in prokaryotes, which are the simplest forms of life, is highly regulated by environmental stimuli. Some examples of stimuli known to regulate gene expression patterns in prokaryotic organisms are light, water, pressure, temperature, etc.
 
        
             
        
        
        
Surface tension decreases when temperature increases because cohesive forces decrease with an increase of molecular thermal activity
        
                    
             
        
        
        
I think its C. global warming
because the other one directly threats aquatic bio diversity while global warming doesn't just affect aquatic biodiversity