Question: In how many different stadiums are the seasons of the 2015 NA Soccer league held?
SPARQL query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT COUNT(?uri) WHERE { ?x onto:league <http://dbpedia.org/resource/2015_North_American_Soccer_League_season> . ?x onto:ground ?uri . ?uri rdf:type onto:Stadium}