Answer: A) Russia suffered almost 80,000 casualties and 90,000 prisoners of war, as compared to Germany's 15,000 casualties.
Additional notes:
The Battle of Tannenburg was a huge loss for Russia. The battle resulted in the near destruction of the Russian Second Army. The Scond Army's commander, General Alexander Samsonov, committed suicide, knowing that the tsar would hold him responsible for the devastating loss.