Which of the following groups,when attached to a benzene ring,acts as a deactivating meta-directing group?

The number of sigma $(\sigma)$ bonds and pi $(\pi)$ bonds in benzene are respectively .......

Which is the correct order for the rate of sulphonation of benzene?

The correct order of the rate of $EAS$ (electrophilic aromatic substitution) for the given compounds is:

Which of the following molecules,in pure form,is (are) unstable at room temperature?
$(A)$ $1,3-$cyclohexadiene
$(B)$ Cyclobutadiene
$(C)$ Cyclopentadienone
$(D)$ Cycloheptatrienone (Tropone)

The reaction ${C_6}{H_6} + C{H_3}Cl \xrightarrow{\text{anhydrous } AlCl_3} {C_6}{H_5}C{H_3} + HCl$ is an example of which of the following?