This is used in organic compounds as key components in the dna molecule and atp

a.nitrogen
b.oxygen
c.carbon
d.phosphorus

Phosphorus is a key component of both ATP and DNA because of their phosphate groups. DNA has one phosphate group with four molecules of phosphorus each per nucleotide. ATP is made up of three phosphate groups with four molecules of phosphorus per each group. While carbon is a good answer, the best answer that specifically pertains to both DNA and ATP is phosphorus.

One possible word that could be used here to fill he blank might be 'evidence'. Science uses evidence to support its explanations. After all, without evidence, any scientific hypotheses is essentially useless and cannot possibly demand acceptance from the wider world.