The correct option is B GATCAATCA
Nucleic acids are polymers of nucleotides. Nucleotides are composed of pentose sugar, phosphoric acid and nitrogenous base. The nitrogenous base can be purine (adenine, guanine) or pyrimidine (cytosine, thymine, uracil). In representation of nucleic acids the bases are generally represented by first alphabet of their names in upper case.