Identify the reagent used in the following conversion:
$CH_3CH_2Cl \xrightarrow{A} CH_3CH_2NO_2$ (Nitroethane)

$A$ bottle containing $C_6H_5I$ and $C_6H_5CH_2I$ has lost its label. To identify them,samples $A$ and $B$ are taken in separate test tubes and boiled with $NaOH$ solution. Finally,the solution in each test tube is acidified with dilute $HNO_3$ and then a few drops of $AgNO_3$ solution are added. Substance $B$ gives a yellow precipitate. Which statement is correct for this process?

Match the following:

Column $I$	Column $II$
$A$. $CH_3-CHBr-CD_3$ on treatment with alc. $KOH$ gives $CH_2=CH-CD_3$ as a major product.	$P$. $E1$ reaction
$B$. $Ph-CHBr-CH_3$ reacts faster than $Ph-CHBr-CD_3$.	$Q$. $E2$ reaction
$C$. $Ph-CH_2-CH_2Br$ on treatment with $C_2H_5OD / C_2H_5O^-$ gives $Ph-CD=CH_2$ as the major product.	$R$. $E1cb$ reaction
$D$. $PhCH_2CH_2Br$ and $PhCD_2CH_2Br$ react with same rate.	$S$. First order reaction

The order of reactivity of alkyl halides for dehydrohalogenation is:

Select the incorrect option:

The increasing order of densities of the following alkyl halides is:
$(I)$ $n-C_3H_7Br$
$(II)$ $n-C_3H_7Cl$
$(III)$ $n-C_3H_7I$