PREFIX acm: <http://sample.com/ont/ACM#> 
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> 

SELECT DISTINCT ?s 
where 
{ GRAPH ?g {?s ?p ?o.
   ?s acm:businessUnit ?businessUnit . 
   }
}
LIMIT 10