Final answer:
The chemical bonds that form between the complementary nitrogenous bases in a DNA double helix are A.hydrogen bonds. Adenine and thymine form two hydrogen bonds, while guanine and cytosine form three hydrogen bonds.
Step-by-step explanation:
In a DNA double helix, hydrogen bonds form between the complementary nitrogenous bases. These hydrogen bonds occur specifically between adenine and thymine, which form two hydrogen bonds, and between guanine and cytosine, which form three hydrogen bonds. The precise alignment of these hydrogen bonds contributes to the stability of the double helix, allowing the DNA to maintain its structure and providing the mechanism for DNA replication and repair. Moreover, the DNA strands are antiparallel and held together by covalent bonds known as phosphodiester linkages, which connect the phosphate of one nucleotide to the sugar of the next.
In summary, the correct answer to the question 'In a DNA double helix, the chemical bonds that form between the complementary nitrogenous bases are _____.' is (c) hydrogen bonds.