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: DAVID BOWIE 
Clue: The film "2001" inspired this song heard here:
"space oddity"

Category: CLEANING UP 
Clue: In 1898 Caleb Johnson sold this soap named for 2 types of oil used to make it; later the co. merged with Colgate
palmolive

Category: DOUBLE THE W 
Clue: There are about 300 species of this tree that usually grows near water

the willow