The substance that is coded for by a length of DNA is base. The correct option is A.
<h3>What is a base?</h3>
Nucleobases, also known as nitrogenous bases or simply bases, are nitrogen-containing biological compounds that form nucleosides, which are then components of nucleotides, all of which are the basic building blocks of nucleic acids.
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The substance that is coded for by a length of DNA is base.
Thus, the correct option is A.
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Biomechanical mechanisms, habitat for plants and animals, participates in cycling of all materials used by living things.