Randomly noticed grammar fix for index.html

Author: TallTed

spec/index.html

@@ -202,7 +202,9 @@ <h3>Graph Statements</h3>
       -->
     </pre>
 
-    <p>A <a data-cite="RDF12-CONCEPTS#dfn-rdf-dataset">RDF dataset</a> may contain a <a data-cite="RDF12-CONCEPTS#dfn-default-graph">default graph</a>, and <a data-cite="RDF12-CONCEPTS#dfn-named-graph">named graphs</a>.</p>
+    <p>An <a data-cite="RDF12-CONCEPTS#dfn-rdf-dataset">RDF dataset</a> may contain a
+      <a data-cite="RDF12-CONCEPTS#dfn-default-graph">default graph</a> and/or zero
+      or more <a data-cite="RDF12-CONCEPTS#dfn-named-graph">named graphs</a>.</p>
 
     <pre id="ex-default-and-named-graphs"
          class="example trig" data-transform="updateExample"