Answer:
The correct answer would be C. cytosine.
It can be explained with the help of complementary nature of nitrogenous base pairs that is, the nitrogenous base of one strand of the DNA (deoxyribonucleic acid) molecule base-pairs specifically with the complementary nitrogenous base of other strand of the DNA.
In DNA , there are four nitrogenous bases namely adenine, guanine, cytosine, and thymine.
Adenine always form base-pair with thymine with the help of two hydrogen bonds.
Similarly, guanine always form base-pair with cytosine with the help of three hydrogen bonds.
