What Accounts for the Uniform Diameter of the DNA Molecule

What accounts for the uniform diameter of the DNA molecule?

A) The two sides of the DNA molecule are held together by hydrogen bonds.
B) A purine always bonds with a pyrimidine.
C) One side of the DNA molecule has an unconnected 5´ phosphate group, and the opposite end has an unconnected 3´ hydroxyl group.
D) The 3´ carbon of one deoxyribose and the 5´ carbon of another deoxyribose bond together.
E) The alternating sugar and phosphate backbone coils around the outside of the helix.