The commercial method of preparation of potassium by reduction of molten $KCl$ with metallic sodium at $850 ^\circ C$ is based on the fact that:

• A
  potassium is solid and sodium distils off at $850 ^\circ C$
• B
  potassium being more volatile and distils off thus shifting the reaction forward
• C
  sodium is more reactive than potassium at $850 ^\circ C$
• D
  sodium has less affinity to chloride ions in the presence of potassium ion