Which of the following has the lowest heat of combustion?

Identify the product $X$ in the following reaction:
$\text{Benzene} + Cl_{2(\text{excess})} \xrightarrow{AlCl_3, \Delta} X$

Identify the heteroatom and the number of double bonds present in furan,respectively.

Which of the following is formed as a result of biological oxidation of benzene in the body of the dog?

Which order is correct for the decreasing reactivity toward ring monobromination of the following compounds:
$I. \, C_6H_5CH_3$
$II. \, C_6H_5COOH$
$III. \, C_6H_6$
$IV. \, C_6H_5NO_2$

Out of benzene,$m$-dinitrobenzene and toluene,which will undergo nitration most easily and why?