Answer:
<h2>Mainly by Hydrogen bonds and the Van der Waals forces
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Explanation:
The DNA double helix (both strands of DNA) are held closs together by i) mainly hydrogen bonds between complementary bases and ii) the Van der Waals base-stacking interaction.
The hydrogen bonds between the base pairs form the double helical structure of DNA. There is no exchange or sharing of electrons in hydrogen bonds.
G always pairs with C with three hydrogen bonds and T always pairs with A with two hydrogen bonds.
Static friction this should help :)