Question: What main language is used in the country that uses Nigerian Naira?
Answer(s):
answer: English Language

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ?c)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
?c ns:location.country.currency_used ns:m.018cg3 . 
?c ns:location.country.official_language ?x .
}