Your nerves send feedback to the brain to tell you what you are touching. I suppose that is a feedback mechanism. I dunno if it is entirely helpful.
        
             
        
        
        
Saprophytes are fungi that are capable of getting nourishment from decaying plants in order to live their lives longer. They are known to stay in rich soil and in various dead trees. They often reside in decaying wood as well.
        
                    
             
        
        
        
In doing these exercises, this is likely to increase the response of the parasympathetic nervous system in which results of making the heart slow and as well as the respiration rate with less muscular tension. The parasympathetic nervous system is the one responsible for conserving energy that makes the heart rate slower, increase the activity of the gland and intestinal activity and as well as relaxing the muscles.
        
             
        
        
        
Answer:
D. A brown gas produced
Explanation:
When a chemical reaction occur, there are several changes that takes place such as change in color, odor change, formation of a gas, and formation of a precipitate etcetera.
In the given chemical reaction, two colorless gas (NO and O2) react together and form brown gas (NO2). So, the change of gas from colorless to brown gas is the evidence that shows chemical reaction occurred.
Hence, the correct option is "D. A brown gas produced".