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: LEGENDS 
Clue: The "Literature Lover's Book of Lists" says this engineer "blew his train whistle in a special way"
casey jones

Category: ALL ABOUT RIVERS 
Clue: You may be waiting for the Robert E. Lee on a natural one of these raised river banks created by flood waters
levee

Category: RELIGION 
Clue: "Mendicant" religious orders made their money the hard way, they did this to earn it

beg