Hydrogen Bonding in C-G Base Pairs

Steps:

• Identify that cytosine (C) pairs with guanine (G) in DNA double helix.
• Recognize that base pairing occurs via hydrogen bonds between complementary bases.
• Recall the specific number: C-G forms three hydrogen bonds, stabilizing the pair.
• Distinguish from backbone bonds: phosphodiester bonds connect nucleotides within strands, not between bases.

Why C is correct:

• Watson-Crick model defines C-G pairing with three hydrogen bonds for structural stability.

Why the others are wrong:

• A: Applies to adenine-thymine pairs, which form only two hydrogen bonds.
• B: Phosphodiester bonds form the sugar-phosphate backbone, not inter-base connections.
• D: Phosphodiester bonds are incorrect type; three is right number but only for hydrogen bonds.

Final answer: C