What is the primary difference between anion-exchange chromatography and cation-exchange chromatography?

• A. Anion-exchange chromatography uses neutral resin to bind neutral proteins, while cation-exchange chromatography uses charged resin to bind charged proteins.
• B. Anion-exchange chromatography uses negatively charged resin to bind positively charged proteins, while cation-exchange chromatography uses positively charged resin to bind negatively charged proteins.
• C. Anion-exchange chromatography uses positively charged resin to bind positively charged proteins, while cation-exchange chromatography uses negatively charged resin to bind negatively charged proteins.
• D. Anion-exchange chromatography uses positively charged resin to bind negatively charged proteins, while cation-exchange chromatography uses negatively charged resin to bind positively charged proteins.

Answer: (D)