$o, p-$ directing groups are mostly

Which of the following reactions takes place when a mixture of concentrated $HNO_3$ and $H_2SO_4$ reacts with benzene at $350 \ K$?

Ozonolysis of $1 \ mol$ of benzene gives .............

In which of the following compounds does the $C-H$ bond exhibit the lowest bond dissociation energy?

Which of these will produce the highest yield in a Friedel-Crafts reaction?

The number of $\sigma$ bonds in $o$-xylene is