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: DUEL 
Clue: In English-speaking countries, once a duel was accepted, this person chose the weapons to be used
the person being challenged

Category: ADMIRALS 
Clue: Opposed to war with the U.S., he nevertheless planned the Japanese attack on Pearl Harbor
isoroku yamamoto

Category: JOHN RITTER 
Clue: John became TV's clown prince of pratfalls as this appropriately named character on "Three's Company"

jack tripper