Question

in a dna molecule, the complementary strands are joined at the nucleotides by hydrogen bonds between what?
a sugars
b nitrogen - containing bases
c phosphates

Explanation:

DNA's complementary strands are held together by hydrogen bonds that form between complementary nitrogen-containing bases (adenine with thymine, guanine with cytosine). Sugars and phosphates make up the backbone of each DNA strand, not the connecting elements between complementary strands.

Answer:

b. nitrogen-containing bases