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.
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Question: Category: DESPOTPOURRI 
Clue: This "Scourge of God" despot is referred to in the "Volsunga Saga" as Atli

Answer: attila


Question: Category: SCIENCE & NATURE 
Clue: Developed by astronomer A.E. Douglass, dendrochronology determines age in this way

Answer: counting tree rings


Question: Category: MARINE SCIENCE 
Clue: Computers can model these, neap type & all, so sailors don't have to rely totally on tables

Answer:
tides