Arrange the compounds $I$,$II$,and $III$ in decreasing order of their heats of combustion.

Provide the bond lengths for hydrogen, ethane, ethene, and ethyne.

The correct statement is

Match the following reactions in List-$I$ with their products in List-$II$:

List-$I$	List-$II$
$A$. The reaction of $1,6$-dibromohexane with $Zn$.	$i$. $H_3C-C \equiv CH$
$B$. Reaction of ethanol with concentrated $H_2SO_4$ at $443 \ K$.	$ii$. $H_2C=CH_2$
$C$. Major product in the reaction of propene with $HBr$ in the presence of benzoyl peroxide.	$iii$. $CH_3-CH_2-CH_2-Br$
$D$. The reaction of $1,1$-dibromopropane with $NaNH_2$ at $433 \ K$.	$iv$. Cyclohexane

$1, 2-$dibromocyclooctane $\xrightarrow[\substack{\text{(ii) } NaNH_2 \\ \text{(iii) } Hg^{2+} / H^{+} \\ \text{(iv) } Zn-Hg / H^{+}}]{\text{(i) } KOH \text{ (alc.) }} \underset{\text{(Major product)}}{P}$. $P$ is

What is the product of $1, 4$-addition in the reaction shown below?