Why are lipids unique when compared to the other macromolecule groups?

Lipids are unique because, they are made from one carbon skeleton unlike the other macro molecules groups which are made from smaller building blocks.
With the exception of steroid hormones, lipids are generally hydrophobic. Also lipids are relative small molecules when compare in size with other macromolecules.

I’d say a : water molecules

The answer is c i just finished taking the test