TASK DEFINITION: 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.
PROBLEM: Category: SIGNS & SYMBOLS 
Clue: Created in 1970 & made up of 3 arrows, the universal symbol for this was based on the Mobius strip

SOLUTION: recycling

PROBLEM: Category: BIBLICAL CITIES 
Clue: Of the 10 most populous U.S. cities, the one that shares its name with a city mentioned in Revelation

SOLUTION: philadelphia

PROBLEM: Category: 18th CENTURY AMERICANS 
Clue: A military post & a Tennessee city are both named for this first U.S. Secretary of War

SOLUTION:
henry knox