instruction:
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 consistency, answers should be in all lower cased letters.
question:
Category: CAN'T SMILE WITHOUT YOU 
Clue: It's the hard outer layer of a tooth
answer:
enamel


question:
Category: KINGS NAMED GUSTAV 
Clue: Current king Carl XVI Gustaf met his wife at this event in Munich in 1972; she was an interpreter
answer:
summer olympics


question:
Category: SCIENCE 
Clue: Every second, fusion reactions in the Sun convert about 600 million tons of this element into helium
answer:

hydrogen