 ( iii ) Every n-vertex unit disk graph has a 2-hop spanner with O(n ^{3/2 ) edges.
<fluency>  ( iii ) Every n-vertex unit disk graph has a 2-hop spanner with O(n ^{3/2 ) edges.
 ( III ) Every n-vertex unit disk graph has a 2-hop spanner with O(n ^{3/2 ) edges.