Which among the given acids has the lowest $pKa$ value?

Which of the following does not show hyperconjugation?

The number of no bond resonance structures possible for but$-1-$ene and a $3^{\circ}$ carbocation having methyl,ethyl,and isobutyl groups on the cationic carbon,respectively,are:

The decreasing order of $-I$ (inductive) effect power for the given groups is:
$A. -CN$
$B. -NO_2$
$C. -NH_2$
$D. -F$

The structure of triphenylmethyl cation is given below. This is very stable and some of its salts can be stored for months. Explain the cause of high stability of this cation.

Given below are two statements:
Statement $I$: In $O_2N-C_6H_4-CH^+-C_6H_4-OCH_3$, the carbocation is stabilised by $+R$ effect of $-OCH_3$ group.
Statement $II$: In $O_2N-C_6H_4-CH^--C_6H_4-OCH_3$, the carbanion is stabilised by $-R$ effect of $-NO_2$ group.
In the light of the above statements, choose the correct answer from the options given below: