Answer:
The correct ansqwer is- Vitamin D
Explanation:
Vitamin D is the vitamin that can be synthesized by the human body itself therefore it is not an essential vitamin for human beings. Human skin is the part that helps in making this vitamin in humans.
The natural form of vitamin D is vitamin D3 which is formed by the sunlight exposure on the skin. When we expose our skin in the sunlight the UV radiation penetrated our skin and converts provitamin D3 into pre-vitamin D3 then this previtamin can be isomerized into the natural form of vitamin D Which is vitamin D3. So the right answer is vitamin D.
 
        
             
        
        
        
I believe the answer is chromosomes.
Chromosomes are basically coiled up pieces of DNA with proteins.
I hope this helps! If it doesn't, please reply.
        
             
        
        
        
Many cells working together forms a tissue.  Many tissues working together forms organs. Many organs working together forms organ systems.  So it goes from general to most specific.  Organ systems are needed in order for life.  This proves that cells are the most basic units of life.
        
                    
             
        
        
        
The temperature increases as you go deeper in the aquatic system.
        
             
        
        
        
Large crystals indicate that it cooled very quickly. If it cooled slowly, it would have time to settle down and make a nice smooth rock.