For an elementary reaction,which of the following is correct?

The reaction rate between two substances $A$ and $B$ is expressed as: $\text{rate} = k[A]^n[B]^m$. If the concentration of $A$ is doubled and the concentration of $B$ is halved,the ratio of the new rate to the initial rate will be:

For the non-stoichiometric reaction $2A + B \to C + D$,the following kinetic data were obtained in three separate experiments,all at $298 \ K$.

Initial Conc. $(A)$	Initial Conc. $(B)$	Initial rate of formation of $C \ (mol \ L^{-1} \ s^{-1})$
$0.1 \ M$	$0.1 \ M$	$1.2 \times 10^{-3}$
$0.1 \ M$	$0.2 \ M$	$1.2 \times 10^{-3}$
$0.2 \ M$	$0.1 \ M$	$2.4 \times 10^{-3}$

For the reaction,the rate of formation of $C$ will be:

For the reaction $H_{2(g)} + Br_{2(g)} \to 2HBr_{(g)}$,the experimental data suggest,$\text{rate} = K[H_2][Br_2]^{1/2}$. The molecularity and order of the reaction are respectively:

What will be the unit of the rate constant for the following reaction?
$C_2H_{4(g)} + H_{2(g)} \rightarrow C_2H_{6(g)}$

The reaction,$X + 2Y + Z \to N$ occurs by the following mechanism:
$(i)$ $X + Y \rightleftharpoons M$ (very rapid equilibrium)
$(ii)$ $M + Z \to P$ (slow)
$(iii)$ $P + Y \to N$ (very fast)
What is the rate law for this reaction?