The vapour of which liquid is present at the upper and lower side of the distillation column?

• A
  The component with the lower boiling point is at the top,and the component with the higher boiling point is at the bottom.
• B
  The component with the higher boiling point is at the top,and the component with the lower boiling point is at the bottom.
• C
  Both components are present in equal amounts at both ends.
• D
  Only the solvent vapour is present at both ends.