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: HUMANITARIAN LADIES 
Clue: Throughout the 1930s, she taught geography at St. Mary's High School in Eastern India

SOLUTION: mother theresa

PROBLEM: Category: TEACHERS ON TV 
Clue: Mr. Novak & Miss Brooks taught this subject

SOLUTION: english

PROBLEM: Category: CHEMISTRY 
Clue: (Sofia of the Clue Crew demonstrates.)  When I put lemon juice on litmus paper, the resulting color tells me where on this scale it belongs

SOLUTION:
the ph scale