Question: What is the main language of the country that has the national anthem "Nigeria, We Hail Thee"?
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.national_anthem ?k .
?k ns:government.national_anthem_of_a_country.anthem ns:m.0w7q9qz . 
?c ns:location.country.official_language ?x .
}