Which of the following statements about lipids is true?
a). Sphingolipids are the most common type of lipids in cellular membranes
b). The passage of steroids and isoprenoids through the membrane is due to the hydrophobic effect
c). Steroids are more likely to be used than other isoprenoids when a flexible structure is required for the function of the lipid
d). Sphingolipids are derived from a combination of fatty acids and serine