I think the statement “the human digestive system is very efficient at squeezing everything it can out of any food?" refers to the way the stomach is good at absorbing the wanted nutrients and keeping them in the body, while disposing of the unwanted waste and toxins. The biomolecules are broken down to preserve only certain nutrients within the molecules.
 
        
                    
             
        
        
        
Answer:
Many scientists use dichotomous keys to identify plants, animals, and other organisms. They may also use dichotomous keys to identify species, or to determine whether a particular organism has been identified and described before. However, dichotomous keys are not used only to identify organisms.
 
        
             
        
        
        
Deforestation is one major concern with harvesting wood. There are also all types of organisms that lose their habitats. 
        
                    
             
        
        
        
 C. transporting nutrients to cells
        
             
        
        
        
the bird is a barn swallow.