What is the correct electron configuration for copper, considering its exception?

• A. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹
• B. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹¹ 4s¹
• C. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁹ 4s²
• D. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s²

Answer: (A)