Question: The public speaker who spoke about Anti-Apartheid was shot by who?
Answer(s):
answer: Lee Harvey Oswald

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:event.public_speaker.speeches_or_presentations ?k .
?k ns:event.speech_or_presentation.speech_topic ns:m.04lxyz0 . 
?c ns:user.alexander.misc.murdered_person.murdered_by ?x .
}