Which of the following is a hydrocarbon?

What are $X$ and $Y$ respectively in the following reactions?

What is the correct order of the rate of nitration for the following compounds?
$A. C_6H_5CH_3, B. C_6H_6, C. C_6D_6, D. C_6T_6, E. C_6H_5Br, F. C_6H_5N^+R_3, G. C_6H_5NMe_2$

Among the following,the aromatic compounds are:
$(A)$ Heptafulvene
$(B)$ Benzene
$(C)$ Cyclopentadienyl anion
$(D)$ Cyclopentadienyl cation
Choose the correct answer from the following options:

The enthalpy of hydrogenation of benzene is $\Delta H_1$ and for cyclohexene is $\Delta H_2$. Then the resonance energy of benzene is:

Which of the following statements are correct?
$I$. In nitrating mixture,nitric acid participates as an acid.
$II$. $\sigma$-complex is the intermediate substance in electrophilic substitution of benzene.
$III$. Benzene on Friedel-Crafts alkylation with $n$-propyl chloride gives isopropyl benzene.