Benzene on nitration gives nitrobenzene in presence of $HN{O}_3$ and $H_{2}S{O}_4$ mixture, where:

$HN{O}_3$ acts as an acid and  $H_{2}S{O}_4$ acts as a base

$HN{O}_3$ acts as a base and $H_{2}S{O}_4$ acts as an acid

Both $H_{2}S{O}_4$ and $HN{O}_3$ act as an acids

Both $H_{2}S{O}_4$ and $HN{O}_3$ act as a bases