How does glutamine's structure differ from asparagine?

• A. Glutamine has an additional hydroxyl group compared to asparagine.
• B. Glutamine has an additional carboxyl group compared to asparagine.
• C. Glutamine has an additional thiol group compared to asparagine.
• D. Glutamine has an additional methylene group (CH2) compared to asparagine.

Answer: (D)