Fractional distillation separates by boiling point Steps:

• Temperature decreases from bottom to top in the fractionating column.
• Lower boiling point fractions rise higher and condense at cooler temperatures.
• X collects higher than Y, indicating X has a lower boiling point.
• Thus, X condenses at a lower temperature than Y.

Why B is correct:

• Condensation temperature equals boiling point; lower for X due to position in column.

Why the others are wrong:

• A: Temperature decreases up the column, not increases.
• C: Longer chains mean higher boiling points, so Y has longer chains than X.
• D: X has a lower boiling point than Y.

Final answer: B