Cells are the basic unit of life and they are the 1st level of organization.  The heart is the 3rd level.  They are separated by 1 level, tissues.
        
             
        
        
        
SO2: inorganic compound
k: element
Cl2: inorganic elemental molecule
C6H6: organic compound
        
                    
             
        
        
        
Answer: air, water, food
, a place to live
Explanation:
The living beings are composed of multiple cells, blood and water. They require certain necessities to survive and reproduce. The air is necessary for respiration. Water is necessary for fulfilling the thirst and maintaining the balance of fluid in the body. Food is necessary as it provides energy to do various biological functions. A place to live is necessary as it is the place where the living being rests, eat food and does other important activities.    
 
        
                    
             
        
        
        
The nucleotide triplet that encodes an amino acid is called a codon. Each group of three nucleotides encodes one amino acid. Since there are 64 combinations of 4 nucleotides taken three at a time and only 20 amino acids, the code is degenerate (more than one codon per amino acid, in most cases).
        
             
        
        
        
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