Answer:
C. a string of nucleotides that can be used as a template to produce a RNA that codes for a protein.
Step-by-step explanation:
A gene is a specific sequence of DNA containing genetic information required to make a specific protien and is a string of nucleotides (DNA in cells) that can be used as a template to produce a RNA (by transcription) that codes for a protein. The produced RNA might be the end product (for example some transfer RNA's) or might be further translated into a protein. An organism's entire complement of DNA is its genome.