Question: Which parent of Martin Luther King Jr died of a heart attack?
Answer(s):
answer: Martin Luther King, Sr.

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.051cc)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.051cc ns:people.person.parents ?x .
?x ns:people.deceased_person.cause_of_death ns:m.0gk4g . 
}