How jena SPARQL results in RDF XML format rather than triple

Question

I wrote SPARQL in String queryString

 "SELECT DISTINCT ?dog ?p ?o " +
            "WHERE {" +
            "?dog <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://test#dog>. " +
            "?dog ?p ?o. " +
            "}";

...

   while (rs_s.hasNext()) {
        QuerySolution qs = rs_s.next();
        String s1 = qs.get("dog").toString();
        String s2 = qs.get("p").toString();
        String s3 = qs.get("o").toString();

As a result, I got a triple format. How do I get it with RDF XML?