In the plasma membrane of a few animals, the presence of cholesterol

The correct option is "enables the membrane to stay fluid more easily when the temperature of the cell drops".

To understand why this is correct, we can look at the role of cholesterol as a fluid buffer in the plasma membrane of animal cells:
At normal body temperatures, cholesterol molecules inserted between phospholipid tails restrict their movement, making the membrane less fluid and more stable.
However, when the temperature drops, phospholipids naturally tend to pack closely together and solidify or freeze into a rigid state, which can disrupt membrane function.

Cholesterol prevents this close packing by wedging itself between the hydrophobic fatty acid chains of the phospholipids.
By disrupting the regular, tight packing of the lipid molecules at lower temperatures, cholesterol lowers the temperature at which the membrane solidifies.
Thus, it acts as a temperature buffer, ensuring that the plasma membrane maintains its essential fluidity and continues to function properly even when the temperature drops.