What structural difference between ddNTPs and normal nucleotides causes termination of DNA synthesis in Sanger sequencing?

• A. Lack of a 3' hydroxyl group in ddNTPs.
• B. Lack of a 5' phosphate group in ddNTPs.
• C. Presence of a methyl group in ddNTPs.
• D. Presence of an extra phosphate group in ddNTPs.

Answer: (A)