The two strands of a DNA double helix are held together primarily by which of the following?

✅Explanation:
-The two strands of a DNA double helix are held together primarily by hydrogen bonds. Hydrogen bonds are weak intermolecular forces that form between a hydrogen atom and an electronegative atom, such as oxygen or nitrogen. In DNA, hydrogen bonds form between the nitrogenous bases on opposite strands. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C). The hydrogen bonds between these base pairs are what hold the two strands of DNA together.

Other options explanations:
-Covalent bonds: Covalent bonds are strong chemical bonds that form between two atoms by the sharing of electrons.
-Hydrophobic interactions: Hydrophobic interactions are weak intermolecular forces that occur between nonpolar molecules and water. Hydrophobic interactions are not involved in holding the two strands of DNA together.
-Ionic interactions: Ionic interactions are strong intermolecular forces that occur between oppositely charged ions. Ionic interactions are not involved in holding the two strands of DNA together.