When Designing a Butter with Higher Ratios of Unsaturated Fats

When designing a butter with higher ratios of unsaturated fats you would need to take care not to remove all saturated fats.What is the main reason for this?

A) Saturated fatty acids are linear in structure and form closely packed structures that are more solid at room temperature.
B) Saturated fatty acids have more carbons in them creating a denser formation at room temperature.
C) The length of saturated fatty acids are longer and interactions with unsaturated fatty acids form solid structures at room temperature.
D) Unsaturated fatty acids on their own would make the butter to hard as they form strong hydrophobic bonds at room temperature.