The answer is the last option. Electronegativity is the measure of the attraction that an atom has for electrons involved in chemical bonds.  It relates to covalent bonds where electrons are shared. The Pauling scale is the most used.
        
                    
             
        
        
        
I'm not sure about 2 but in 3 it would float
        
             
        
        
        
Valency- it means the combing capacity if an element.
<span> radical- it  is an atom, molecule, or ion that has unpaired valence electrons or an open electron shell.
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The nervous system sends signals to the muscles to shiver when our body temperature begins to drop to a lower than normal temperature. the slight movement of the muscles will work to bring temperature back to homeostasis