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: PARTICLE PHYSICS 
Clue: To get an element's mass number, add its protons & these

SOLUTION: neutrons

PROBLEM: Category: THE LAST CATEGORY 
Clue: This "Home Run King" played in his 3,298th & last game for the Milwaukee Brewers in 1976

SOLUTION: hank aaron

PROBLEM: Category: BASEBALL 
Clue: Tony Gwynn of this National League team has the highest career average of all active players with .340

SOLUTION:
san diego padres