What is the order of reaction for the decomposition of gaseous acetaldehyde?

For the reaction $2A + 2B \rightarrow 2C + D$,if $r = k[A]^2[B]^0$,then the rate of reaction is:

The hydrolysis of an ester is catalyzed by dilute acids $A$ and $B$. The rate constants for the two processes are $K_A$ and $K_B$ respectively. If $K_A > K_B$,which of the following statements is correct?

For the reaction $Cl_{2(aq)} + H_2S_{(aq)} \to S_{(s)} + 2H^{+}_{(aq)} + 2Cl^{-}_{(aq)}$,the rate law is $r = K[Cl_2][H_2S]$. Which of the following mechanisms is/are consistent with this rate law?
$A. \ H_2S \rightleftharpoons H^{+} + HS^{-}$ (fast)
$Cl_2 + HS^{-} \to 2Cl^{-} + H^{+} + S$ (slow)
$B. \ Cl_2 + H_2S \to H^{+} + Cl^{-} + Cl^{+} + HS^{-}$ (slow)
$Cl^{+} + HS^{-} \to H^{+} + Cl^{-} + S$ (fast)

For the reaction $A \to xP$,when $[A] = 2.2 \, mM$,the rate was found to be $2.4 \, mM \, s^{-1}$. On reducing the concentration of $A$ to half,the rate changes to $0.6 \, mM \, s^{-1}$. The order of reaction with respect to $A$ is

For the chemical reaction $2O_3 \rightarrow 3O_2$,the mechanism is given below. What will be the rate law expression?
$O_3 \rightleftharpoons O_2 + O$ ...... (fast)
$O + O_3 \rightarrow 2O_2$ ...... (slow)