Which of the following is a reasonable explanation for why unsaturated fatty acids keep any membrane more fluid at lower temperatures?

a) the double bonds block interaction among the hydrophilic head groups of the lipids.
b) the double bonds result in shorter fatty acid tails and thinner membranes.
c) unsaturated fatty acids are more polar than saturated fatty acids.
d) unsaturated fatty acids have a higher cholesterol content and therefore more cholesterol in membranes.
e) the double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.