The incorrect relation for isohydric solutions is $:-$

Given below are two statements :
Statement $I$ : Aqueous solution of ammonium carbonate is basic.
Statement $II$ : Acidic/basic nature of salt solution of a salt of weak acid and weak base depends on $K_a$ and $K_b$ value of acid and the base forming it.
In the light of the above statements,choose the most appropriate answer from the options given below :

What is the percent dissociation of $NH_4OH$ if the molar conductance at zero concentration for $NH_4Cl, NaCl$,and $NaOH$ are $130, 109$,and $213 \ S \ cm^2 \ mol^{-1}$ respectively,and the molar conductivity of $0.01 \ M \ NH_4OH$ is $9.0 \ S \ cm^2 \ mol^{-1}$?

At $25 \, ^oC$,the concentration of $H^{+}$ and $OH^{-}$ ions in pure water is $1 \times 10^{-7} \, M$ each. Which of the following is equal to $2 \times 10^{-7} \, M$?

If $0.1 \, M, 100 \, mL$ $NaOH$ solution is mixed with $0.05 \, M, 100 \, mL$ $H_2SO_4$ solution,the $pH$ of the resulting solution is:

$A$ solution of $0.1 \ M$ weak base $(B)$ is titrated with $0.1 \ M$ of a strong acid $(HA)$. The variation of $pH$ of the solution with the volume of $HA$ added is shown in the figure below. What is the $pK_{b}$ of the base? The neutralization reaction is given by $B + HA \rightarrow BH^{+} + A^{-}$.