What is the number of $\pi$ electrons present in pyridine?

Given below are two statements $:$
Statement $(I) :$ On nitration of $m-$xylene with $HNO_3, H_2SO_4$ followed by oxidation,$4-$nitrobenzene$-1, 3-$dicarboxylic acid is obtained as the major product.
Statement $(II) :$ $-CH_3$ group is $o/p-$directing while $-NO_2$ group is $m-$directing group.
In the light of the above statements,choose the correct answer from the options given below $:$

Which of the following compounds is most reactive towards electrophilic nitration?

The correct order of reactivity towards the electrophilic substitution of the compounds aniline $(I)$,benzene $(II)$,and nitrobenzene $(III)$ is

In which of the following compounds does the $C-H$ bond exhibit the lowest bond dissociation energy?

According to $H$ückel's rule, a cyclic $\pi$-molecular orbital system must contain which of the following to be aromatic?