Question: Which mountain with a prominence of 91.0 can you find the start of the Delaware river?
Answer(s):
answer: Mount Jefferson

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.0dtzd)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.0dtzd ns:geography.river.origin ?x .
?x ns:geography.mountain.prominence "91.0" . 
}