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: DRAMA 
Clue: Sula & Helena are robotesses in this Karel Capek play

SOLUTION: "r.u.r."

PROBLEM: Category: MUSIC 
Clue: Webster's defines this word as "a chord of three tones consisting of a root with its third and fifth"

SOLUTION: a triad

PROBLEM: Category: TRANSPORTATION 
Clue: An aircraft that can take off & touch down on water or land is called this, like a class of animals

SOLUTION:
amphibious