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