challenge: What was DNA Tower commissioned to commemorate?
  
  A. The 50th anniversary of the discovery of the structure of the DNA molecule and the 100th anniversary of the IU School of Nursing
  B. The 100th anniversary of the IU School of Engineering and the 50th anniversary of the discovery of the polio vaccine
  C. The 100th anniversary of the IU School of Medicine and the 50th anniversary of the discovery of the structure of the DNA molecule
  D. The 50th anniversary of the discovery of penicillin and the 100th anniversary of the IU School of Pharmacy
  Answer: 