Question

which statement best describes how the strands were separated?○ covalent bonds were broken by an enzyme to separate the nitrogen bases.○ hydrogen bonds were broken by an enzyme to separate the nitrogen bases.○ covalent bonds were broken by an enzyme to separate the sugar and phosphate groups.○ hydrogen bonds were broken by an enzyme to separate the sugar and phosphate groups.

Explanation:

DNA strands are held together by hydrogen bonds between complementary nitrogenous base pairs (A-T, G-C). Helicase, the enzyme that separates DNA strands, breaks these hydrogen bonds, not the covalent bonds that link sugar and phosphate groups in the DNA backbone.

Answer:

Hydrogen bonds were broken by an enzyme to separate the nitrogen bases.