Question

how do unsaturated fatty acids help keep any membrane more fluid at lower temperatures?
the double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing tightly together.
unsaturated fatty acids have a higher cholesterol content that prevents adjacent lipids from packing tightly together.
unsaturated fatty acids are more polar than saturated fatty acids.
the double bonds result in shorter fatty acid tails and therefore thinner membranes.

Explanation:

Unsaturated fatty acids have double bonds. These double bonds create kinks in the fatty acid tails. At lower temperatures, these kinks prevent adjacent lipids from packing tightly together. This keeps the membrane more fluid. Cholesterol content is not related to unsaturated fatty acids in this context. Unsaturated fatty acids are not more polar than saturated ones. Double bonds do not make fatty - acid tails shorter.

Answer:

the double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing tightly together.