The compound with molecular formula $C_6H_6$,which gives only one monobromo derivative and takes up four moles of hydrogen per mole for complete hydrogenation,has $................\pi$ electrons.

"$P$" is a hydrocarbon with the molecular formula $C_8H_{14}$. On ozonolysis,"$P$" forms "$Q$". "$Q$" on treatment with alkali under reflux conditions produces "$R$",which on treatment with $I_2/NaOH$ gives a yellow precipitate. Acidification of the solution gives "$S$". The structure of "$S$" is given below:
(Structure $S$: $1-$methyl$-2-$oxocyclopentanecarboxylic acid derivative or similar cyclic structure as per common reaction pathways).
The correct structure of "$P$" is:

$A$ petroleum fraction having a boiling range of $70-200 \ ^\circ C$ and containing $6-10$ carbon atoms per molecule is called:

Which of the following compounds was the starting material for the oxidation shown below?

Which of the following is aromatic?

The decreasing order of heat evolved upon catalytic hydrogenation of the given reactants with $H_2\ (Pd/C)$ is: