Primary alcohols on dehydration give

The major product of the following reaction is:

The reaction shown in the image proceeds by the $.......$ mechanism.
$CH_3CH_2CH(OH)CH_3 + SOCl_2 \rightarrow CH_3CH_2CH(Cl)CH_3 + SO_2 + HCl$

In the given reaction: $CH_3-CH(OH)-C(OH)(CH_3)_2 \xrightarrow{HIO_4} (a) + (b)$. $(a)$ and $(b)$ respectively are:

$X + HCl$ $\xrightarrow[\text{Addition}]{\text{Anhy. } AlCl_3} C_2H_5Cl \xleftarrow[\text{Substitution}]{\text{Anhy. } ZnCl_2/HCl} Y$. The conversion of $Y$ to $X$ can be achieved by heating with .......... at .......... temperature.

The major product formed in the following transformation is most likely to be