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 consistency, answers should be in all lower cased letters.
PROBLEM: Category: SCIENCE GUYS 
Clue: Eugene Dubois died in 1940 still believing his "Java Man" to be this legendary connector between man & ape

SOLUTION: the missing link

PROBLEM: Category: ECONOMICS 
Clue: After deducting all expenses from your gross profit, you're left with this

SOLUTION: net

PROBLEM: Category: MEMBER NATIONS OF OPEC 
Clue: Until it withdrew in 2008, the only far east nation in OPEC was this large one made up of thousands of islands

SOLUTION:
indonesia