Why are replication origins typically rich in adenine and thymine?

• A. Adenine and thymine are the only bases found in replication origins.
• B. Adenine and thymine are more stable than guanine and cytosine.
• C. Replication origins are randomly composed of adenine and thymine.
• D. Adenine and thymine have fewer hydrogen bonds, making them easier to separate.

Answer: (D)