Which of the following statements is true about lipids?
a) Sterols have 8 carbon atoms and include cholesterol and vitamin D.
b) Bile acids and their salts have 5 carbon atoms.
c) Progesterone and adrenal steroids have 2 carbon atoms.
d) Sex hormones have no carbon atoms.

a) Only a is correct.
b) Only b is correct.
c) Only c is correct.
d) Only d is correct.