Answer:
Due to the presence of three hydrogen bonds.
Step-by-step explanation:
DNA or deoxyriboucleic acid is made up of polymers of nucleotide. The single nucleotide consists of a nitrogenous base, a pentose deoxyribose sugar and a phosphate group.
The nitrogenous bases are adenine, guanine, thymine and cytosine. Adenine is bonded with thymine with two hydrogen bonds whereas cytosine is bonded with guanine with three hydrogen bonds. Three hydrogen bonds are difficult to break as compared with two hydrogen bonds. Hence, DNA with more GC content is difficult to denature.