When $(X)$ reacts with $(Y)$ in the presence of dilute $(Z)$ solution,$3-$hydroxybutanal is formed. What are $(X), (Y),$ and $(Z)$?

Hex$-4-$en$-2-$ol on treatment with $PCC$ gives $'A'.$ $'A'$ on reaction with sodium hypoiodite gives $'B',$ which on further heating with soda lime gives $'C'.$ The compound $'C'$ is $....... .$

Which of the following is the correct statement for the given reaction?
$CH_3-CH=O + C_6H_5-CH=O \xrightarrow[\Delta]{OH^{\ominus}(aq)} X_{(C_4H_6O)} + Y_{(C_9H_8O)}$

Consider the following reaction,where:
$(A)$ The change in the functional group and
$(B)$ The corresponding change in the hybridization from the starting material to the final product are:
$CH_3-C \equiv N \xrightarrow[(ii) \ HI + \text{Red } P]{(i) \ SnCl_2, HCl / H_3O^{+}}$

Ethyl ester $\xrightarrow{CH_3MgBr} P$. What will be the product $P$?

The major product $X$ formed in the following reaction is: