Membranes with unsaturated fatty acids in their components are more flexible and fluid because: a. unsaturated fatty acids pack closely together to form ordered arrays. b. unsaturated fatty acids bend at the double bond preventing close packing. c. saturated fatty acids have a "kink" that produces more fluid aggregates. d. unsaturated fatty acids have cis double bonds that prevent formation of the "kink." e. all of the above are correct.