You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

[Q]: Category: THE NATIONAL MUSEUM OF HEALTH & MEDICINE 
Clue: Among lesser-known body parts at the museum, see the leg Gen. Daniel Sickles lost at this July 1863 battle
[A]: gettysburg


[Q]: Category: THE "I"s HAVE IT 
Clue: In a proverb, it's "no excuse" for breaking the law
[A]: ignorance


[Q]: Category: VIRAL VIDEO 
Clue: nationalgeographic.com has a video about how this disease softened up the Inca, easing the Spanish conquest
[A]:
smallpox