What holds the two strands of a DNA molecule together? A. Ionic bonds between negatively and positively charged ionsB. Covalent bonds between sugars and phosphatesC. Brüno's interactionsD. Hydrogen bonds between complementary base pairs

D. Hydrogen bonds between complementary base pairs89

Explanation:

A DNA molecule is composed of two long polynucleotide chains made of four types of nucleotide subunits, two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). These nucleotides are joined by covalent bonds forming a phosphate-sugar backbone. These strands are held to one another with hydrogen bonds between the base portions of complementary nucleotides.

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