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.

Category: YOUNG PEOPLE WHO MADE A DIFFERENCE 
Clue: Born near what became Jamestown, Virginia around 1595, her name meant "playful one"
pocahontas

Category: HISTORY 
Clue: In June 1987 she became the first British prime minister in the 20th c. elected to 3 straight terms
margaret thatcher

Category: DOUBLE LETTERS 
Clue: It's any heavy material placed in the gondola of a balloon or the hold of a ship to enhance stability

a ballast