$A$ student has studied the decomposition of a gas $AB_3$ at $25^{\circ} C$. He obtained the following data.

$p \ (mm \ Hg)$	$50$	$100$	$200$	$400$
Relative $t_{1/2} \ (s)$	$4$	$2$	$1$	$0.5$

The order of the reaction is

The rate law for the decomposition of hydrogen iodide is $-\frac{d[HI]}{dt}=k[HI]^2$. The units of rate constant $k$ are

The rate law equation for a reaction between $A$,$B$ and $C$ is $r = k[A][B][C]^2$. What will be the new rate of reaction if the concentration of both $A$ and $B$ are doubled (in $r$)?

The following reactions occur for the reaction of $NO$ with $Br_2$ to form $NOBr$:
$NO_{(g)} + Br_{2_{(g)}} \rightleftharpoons NOBr_{2_{(g)}}$
$NOBr_{2_{(g)}} + NO_{(g)} \rightarrow 2 NOBr_{(g)}$
If the second reaction is the rate-determining step,the order of the reaction with respect to $NO_{(g)}$ will be:

During the kinetic study of the reaction $2A + B \rightarrow C + D$,the following results were obtained:

Experiment	$[A] \ (M), [B] \ (M)$ and Initial rate of formation of $D$
$i. \ [A]=0.1, [B]=0.1$	$6.0 \times 10^{-3} \ M \ s^{-1}$
$ii. \ [A]=0.3, [B]=0.2$	$7.2 \times 10^{-2} \ M \ s^{-1}$
$iii. \ [A]=0.3, [B]=0.4$	$2.88 \times 10^{-1} \ M \ s^{-1}$
$iv. \ [A]=0.4, [B]=0.1$	$2.40 \times 10^{-2} \ M \ s^{-1}$

Based on the above data,the overall order of the reaction is:

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