Answer:
What do I do with this information? XD
 
        
                    
             
        
        
        
The answer would be D. Empiricality. Scientific Method can not, and will not deal with studies that are either for logic or for theism. This field may be beyond the scientific confirmability, meaning, it can not be proven by science, one example of this is the existence of a primary mover, or a God.
        
             
        
        
        
Animals absorb oxygen and release carbon dioxide in respiration and plants absorb carbon dioxide and release oxygen through photosynthesis.
 
        
             
        
        
        
Answer:
Blood Brain Barrier(BBB)
Explanation:
This is a biological interface of special endothelial cells of astrocytes, pericytes , capillaries,  neurons and other  structures, acting as a physical barrier or  gate separating the Central Nervous system from the peripheral  blood circulations. Thus it  formed a tight junction serving as a  physical barrier to  selectively regulate the entrance of substances from the   cerebral blood flow   into the brain,  therefore maintaining homeostasis of the brain.
From above any  substances  absorbed into the blood stream  irrespective of the mode of entry  are transported through  the BBB, and  are selectively  regulated to enter the brain cells by the BBB's   interactions with the blood vessels, hormones etc. 
Basically it allows the passage of nutrients,  a few  drug, hormones and resists certain toxins and pathogens for the brain homeostasis.