Consider the reaction : $\mathrm{Cl}_{2}(a q)+\mathrm{H}_{2} \mathrm{~S}(a q) \rightarrow$ $\mathrm{S}(s)+2 \mathrm{H}^{+}(a q)+2 \mathrm{Cl}^{-}(a q)$ The rate equation for this reaction is rate $=k\left[\mathrm{Cl}_{2}\right]\left[\mathrm{H}_{2} \mathrm{~S}\right]$ Which of these mechanisms is/are consistent with this rate equation? A. $\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{~S} \rightarrow \mathrm{H}^{+}+\mathrm{Cl}^{-}+\mathrm{Cl}^{+}+\mathrm{HS}^{-}$ (slow) $\mathrm{Cl}^{+}+\mathrm{HS}^{-} \rightarrow \mathrm{H}^{+}+\mathrm{Cl}^{-}+\mathrm{S}$ B. $\mathrm{H}_{2} \mathrm{~S} \rightleftharpoons \mathrm{H}^{+}+\mathrm{HS}^{-}$ (fast equilibrium) $\mathrm{Cl}_{2}+\mathrm{HS}^{-} \rightarrow 2 \mathrm{Cl}^{-}+\mathrm{H}^{+}+\mathrm{S}$ (Slow)

• A

  $\mathrm{B}$ only
• B

  $\quad$ Both $\mathrm{A}$ and $\mathrm{B}$
• C

  Neither A nor B
• Correct answer
  D

  A only

Hence, the correct answer is option: 'D'.