Which statement correctly describes why a compound is a pure substance?

They are like other investigations? say there was a murder u have to do blood test and finger prints which run through a lab. 

It will appear as o2(g) as a reactant 

Answer it was we, the the whole people, who formed the union. and we formed it, not to give the blessings of liberty, but to secure them: not to the half of ourselves and the half of our posterity, but to the whole people- women as well as men.