Nucleic Acids Have a Definite Polarity, or Directionality

Multiple Choice

Nucleic acids have a definite polarity, or directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described?

A) One end has an unlinked 3 carbon; the other end has an unlinked 5 carbon.
B) One end has one phosphate group; the other end has two phosphate groups.
C) One end contains a nitrogenous base; the other end lacks it.
D) One end has a hydroxyl group on the 2 carbon; the other end has a hydrogen atom on the 2 carbon.