Molten sodium chloride conducts electricity due to the presence of

The half-life of a radioactive substance against $\alpha$-decay is $1.2 \times 10^7 \ s$. What is the decay rate for $4 \times 10^{15}$ atoms of the substance?

Consider the reaction:
$Cl_{2(aq)} + H_2S_{(aq)} \to S_{(s)} + 2H^{+}_{(aq)} + 2Cl^{-}_{(aq)}$
The rate equation for this reaction is $\text{rate} = k[Cl_2][H_2S]$. Which of these mechanisms is/are consistent with this rate equation?
$A.$ $Cl_2 + H_2S \to H^{+} + Cl^{-} + Cl^{+} + HS^{-}$ (slow)
$Cl^{+} + HS^{-} \to H^{+} + Cl^{-} + S$ (fast)
$B.$ $H_2S \rightleftharpoons H^{+} + HS^{-}$ (fast equilibrium)
$Cl_2 + HS^{-} \to 2Cl^{-} + H^{+} + S$ (slow)

The binding energy per nucleon versus mass number curve for nuclei is shown in the figure. $W, X, Y$ and $Z$ are four nuclei indicated on the curve. The process that would release energy is

Root cap is absent in

The order of reactivity of phenol $(I)$,nitrobenzene $(II)$ and benzene $(III)$ towards nitration is