Which of the following pairs of $2,3-$butanediol are enantiomers?

• A
  $2R, 3R$ and $2S, 3S$
• B
  $2S, 3S$ and $2S, 3R$
• C
  $2R, 3R$ and $2R, 3S$
• D
  $2S, 3S$ and $2R, 3S$