instruction:
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.
question:
Category: PSYCHOLOGY TERMS 
Clue: This 2-word term has its origins in a hostage-taking that followed the botched 1973 Norrmalmstorg bank robbery
answer:
stockholm syndrome


question:
Category: POLITICAL PHILOSOPHY 
Clue: The subtitle of this influential 1762 treatise is "Principes du droit politique" ("Principles of Political Right")
answer:
the social contract


question:
Category: PAINTINGS 
Clue: The alternate name of this 16th century Italian painting also means "cheerful"
answer:

the mona lisa