Answer:
Guanine.
Step-by-step explanation:
DNA is present as genetic material of all the organism.DNA is made of the four different nitrogenous bases, pentose deoxyribose sugar and the phosphate group.
DNA is complimentary in nature in which the nitrogenous bases combine specifically with each other. Adenine binds with cytosine with two hydrogen bonds and guanine binds with cytosine with three hydrogen bonds.
Thus, the answer is guanine.