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.

[EX Q]: Category: WORLD GEOGRAPHY 
Clue: The name of this large port city on Western Europe's Schelde River literally means "at the wharf"
[EX A]: antwerp

[EX Q]: 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
[EX A]: levee

[EX Q]: Category: WORLD GEOGRAPHY 
Clue: This river is only navigable for about 80 miles, from Lisbon to Abrantes, Portugal
[EX A]:
tagus