What is the correct order of $o/p$ ratio when $E^{+}$ attacks the following systems?
$(A): Ph-F, (B): Ph-Cl, (C): Ph-Br, (D): Ph-I$

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile,$E^{+}$:
$(a)$ Chlorobenzene,$2,4-$dinitrochlorobenzene,$p-$nitrochlorobenzene
$(b)$ Toluene,$p-CH_3-C_6H_4-NO_2$,$p-O_2N-C_6H_4-NO_2$

Which of the following reasons support that aryl halides are less reactive than alkyl halides towards nucleophilic substitution reactions?
$a)$ The formation of more stable arenium ion
$b)$ Partial double bond character of $C-X$ bond
$c)$ Longer $C-X$ bond
$d)$ $sp^2$ carbon bonded to $X$ is more electronegative

The $C-Cl$ bond lengths (in $pm$) in haloarene and haloalkane are respectively:

"The presence of an electron-withdrawing group $\left( -NO_2 \right)$ at the ortho and para positions in haloarenes increases the reactivity of haloarenes towards nucleophilic substitution reactions." Prove this with an example.

Amongst the following,the compound that is nitrated with difficulty is