ASK WHERE { <http://dbpedia.org/resource/Karl_Marx> <http://dbpedia.org/ontology/mainInterest> <http://dbpedia.org/resource/Labor_relations> }
Is Labor relations the main interest of Karl Marx?
ASK WHERE { resource:Karl_Marx property:main_interest resource:Labor_relations }
Yes
[Yes], Labor relations is the main interest of Karl Marx.
Yes, labor relations are the major interest of Karl Marx.
[Yes], Labor relations is  the main interest of him.
[Yes] industrial relations is his main interest.