One of the most abiotic factor that may affect humans directly is waster availability because with out water we can get dehydrated and die.
        
             
        
        
        
The CNS involves the brain and spinal cord and the PNS involves the body nerves.
        
                    
             
        
        
        
Answer:
You multiply 0.5 by 20 which will give you 10 your answer is 10