Two Double-Stranded Fragments of DNA Are Exactly the Same Length

Two double-stranded fragments of DNA are exactly the same length. At 89°C, fragment A has completely denatured, which means that the two strands have separated. At that temperature, fragment B is still double-stranded. How might these fragments differ to result in different denaturation temperatures?

A) Fragment A has a higher C+C content than fragment B.
B) Fragment B has a higher C+G content than fragment A.
C) Fragment A has a secondary structure of B form, while fragment B is an A form.
D) Fragment B is methylated more than fragment A.