When benzyl alcohol is oxidised with $KMnO_4$,the product obtained is

Which of the following compounds on oxidation gives ethyl methyl ketone?

Ethylene glycol,on oxidation with periodic acid $(HIO_4)$,gives:

In the following reaction,'$B$' is

Consider the following reaction sequence:
$C_6H_5-CH=CH-CHO$ $\xrightarrow[35^{\circ}C]{LiAlH_4} A$ $\xrightarrow[Excess]{CH_3MgBr} B$
Identify $B$ in the reaction.

The product obtained by heating ethanol with concentrated $H_2SO_4$ at $165^{\circ}C - 170^{\circ}C$ is: