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.
--------
Question: Category: CHEMISTRY 
Clue: It's a system of small particles "hanging" in a liquid; paint, for example

Answer: suspension


Question: Category: TO REMAIN "SILENT" 
Clue: Quiet alliterative nickname of the U.S. Navy's submarine fleet

Answer: the silent service


Question: Category: "CUS" WORDS 
Clue: Parents living together have the joint type of this, & may continue to have it after a divorce

Answer:
custody