Overrotation or Underrotation of a DNA Double Helix Places Strain

Overrotation or underrotation of a DNA double helix places strain on the molecule, causing it to supercoil. Supercoiling is controlled by topoisomerase enzymes. Most cellular DNA is negatively supercoiled, which eases the separation of nucleotide strands during replication and transcription and allows DNA to be packed into small spaces.
-A DNA molecule 300 bp long has 20 complete rotations. This DNA molecule is

A) positively supercoiled.
B) negatively supercoiled
C) relaxed.