The 5 $\rightarrow$ 3' Orientation of a DNA or RNA Chain Refers to Chain

The 5' $\rightarrow$ 3' orientation of a DNA or RNA chain refers to the:

A) linkage of the phosphodiester bonds between the nucleotides.
B) location of the attachment of the nitrogenous base on the pentose sugar.
C) positions of the chain that do not have a nucleotide attached.
D) positions of the chain that do not have a phosphate group attached.
E) respective net charges found at each end of the chain.