Which of the following is called as Mandelonitrile?

Which of the following reactants on reaction with conc. $NaOH$ followed by acidification gives the following lactone as the only product?

In the reaction,$C_6H_5COCH_3 \xrightarrow[Zn-Hg / \text{conc. } HCl]{[H]} X$,$X$ is

In the reaction $CH_3CH_2OH \xrightarrow{OH^-} CH_3CHO$,which carbon atom undergoes oxidation?

$CH_3-CHO$ $\xrightarrow[OH^{-}]{HCN} (A)$ $\xrightarrow{\text{Partial Hydrolysis}} (B)$. Product $B$ is:

$A$ compound $A$ has a molecular formula $C_2Cl_3OH$. It reduces Fehling's solution and on oxidation gives a monocarboxylic acid $(B)$. $A$ is obtained by the action of chlorine on ethyl alcohol. $A$ is: