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

Consider the reaction sequence below:
Anisole $\xrightarrow[AlCl_3]{\text{Succinic anhydride}} A$ $\xrightarrow[\text{Clemmensen's reduction}]{\text{Cyclization}} X$
Identify $X$.

The starting material for the preparation of styrene is

$n$-Butylbenzene on oxidation with hot alkaline $KMnO_4$ gives

Which one of these is not true for benzene?

Which of the following has the lowest heat of combustion?