by 
Thommy
ANSWERS: 1
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1) "By mass, human cells consist of 65–90% water (H2O), and a significant portion is composed of carbon-containing organic molecules. Oxygen therefore contributes a majority of a human body's mass, followed by carbon. 99% of the mass of the human body is made up of the six elements oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus." Source and further information: http://en.wikipedia.org/wiki/Composition_of_the_human_body 2) "In general, organisms are made up of about 25 of the elements in the top four rows of the periodic table." Source and further information: http://science-class.net/Chemistry/Atoms/chemistryreview.pdf
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