The presence of unsaturation in organic compounds can be tested with

$cis-3-hexene \xrightarrow{(a)} \text{meso } 3,4-hexanediol$
$trans-3-hexene \xrightarrow{(b)} \text{meso } 3,4-hexanediol$
Choose the pair of reagents $(a, b)$ for the above conversions.

Consider compounds $A$, $B$, and $C$ with the following structural formulae:
$A = CH_3 - CH_2 - CH_2 - CH_2 - CH_2 - OH$
$B = CH_2 = CH - CH_2 - CH_2 - CH_3$
$C = HO - CH_2 - CH_2 - CH(OH) - CH_3$
For the conversion of $B$ from $A$, the reagent $(D)$ required is . . . . . . and the structural formula of the product $(E)$ obtained when $C$ undergoes the same reaction using excess reagent $(D)$ is . . . . . . .

In the reaction $CH_2 = CH_2$ $\xrightarrow[\text{acid}]{\text{Hypochlorous}} M$ $\xrightarrow{R} \begin{array}{c} CH_2OH \\ | \\ CH_2OH \end{array}$,$M$ and $R$ are respectively:

Which hydrogen in compound $(E)$ is easily replaceable during bromination reaction in the presence of light?
$CH_3 - CH_2 - CH = CH_2$
$(E)$

Which of the following reagents reacts with $but-1-ene$ to give an optically inactive product?