Factors Increasing Membrane Fluidity at Low Temperatures Steps:

• Identify factors: 1) unsaturated fatty acids introduce kinks, preventing tight packing; 2) shorter fatty acid chains reduce van der Waals interactions; 3) cholesterol disrupts phospholipid alignment, acting as a buffer.
• At low temperatures, membranes gel; these factors maintain disorder.
• Evaluate combinations: all three counteract gel phase effectively.
• Select option including all: A covers 1, 2, and 3.

Why A is correct:

• All three factors reduce packing density, increasing fluidity per fluid mosaic model.

Why the others are wrong:

• B excludes 2, missing shorter chains' role.
• C excludes 2 and 3, incomplete.
• D excludes 1, ignoring unsaturation's kinks.

Final answer: A