Answer:
Mechanical barriers — which include the skin , mucous membranes , and fluids such as tears and urine — physically block pathogens from entering the body. Chemical barriers — such as enzymes in sweat , saliva , and semen — kill pathogens on body surfaces.
 
        
                    
             
        
        
        
90% of the available energy is lost in some form of heat, transferring light energy into different living organisms 
        
                    
             
        
        
        
The answer is C. Adapting to changes in the environment
        
             
        
        
        
It's a decomposition reaction. It's a chemical reaction because one substance (H2O2) is breaking down and becoming 2 completely new substances (H2O and O2)