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: 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

SOLUTION: palmolive

PROBLEM: Category: HOUSEPLANTS 
Clue: Roots sticking through drainage holes in containers are a sign that it's time to do this

SOLUTION: re-pot

PROBLEM: Category: PREFIXES 
Clue: Contra-

SOLUTION:
against