Option D is correct.
A synapse is the opening between neurons that neurotransmitters pass through.
        
                    
             
        
        
        
Http://www.collective-evolution.com/2014/07/07/new-study-finds-88-percent-of-earths-ocean-surface-no...
This should be of use here. 
        
             
        
        
        
A species could gain negative traits through evolution. So, evolution does not always mean progress.
 
        
             
        
        
        
Compounds are made up of molecules