The correct answer is a - GTCCAATGC
According to base pairing rules, in DNA G will always pair with C and A will always pair with T.
These letters represent nucleotides. Nucleotides are the building blocks of nucleic acids namely DNA and RNA.
A denotes the nucleotide called Adenine
C denotes the nucleotide called Cytosine
G denotes the nucleotide called Guanine
T denotes the nucleotide called Thymine.
In RNA, there is slight difference in base pairing. Since RNA never has Thymine in its structure, the thymine has been replaced with Uracil. Therefore in RNA, Adenine will pair with Uracil.