Question: Which political systems are used in the country where the Nigerian naira is the currency?
Answer(s):
answer: Presidential system
answer: Federal republic

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.form_of_government ?x .
}