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.

Category: THE ENVIRONMENT 
Clue: This word means catching an unsustainably high number of tuna & cod
overfishing

Category: THE 19th CENTURY 
Clue: 1853 purchase that brought the contiguous U.S. about up to its present area
the gadsden purchase

Category: SICKNESS & HEALTH 
Clue: Emotional instability & irritability are symptoms of this condition abbreviated PMS

pre-menstrual syndrome