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.
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Question: Category: COUNTRIES OF THE WORLD 
Clue: The 3 most populous countries, they added up to an estimated 2.42 billion people in 1996

Answer: china, india, & the usa


Question: Category: U.S. GEOGRAPHY 
Clue: Of the USA's 50 tallest peaks, all are in Alaska, Colorado & California except this peak

Answer: mt. rainier


Question: Category: MODERN TECHNOLOGY 
Clue: Common name given Douglas Engelbart's device, an "X-Y position indicator for a display system"

Answer:
mouse