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: QUICK BIOS 
Clue: Born near Gzhatsk in 1934; promoted to major in 1961 shortly before liftoff, just in case; died 1968

SOLUTION: yuri gagarin

PROBLEM: Category: DIGESTION 
Clue: This substance in your food slows down the digestive process & is what bile works on

SOLUTION: fat

PROBLEM: Category: MATH TERMS 
Clue: The term surd refers to irrational numbers like this number's square root, 1.7320508...

SOLUTION:
3