When ethanol is treated with sulphuric acid at $413 \ K$,the reaction involved in it is:

Compound $A$ of molecular formula $C_4H_{10}O$ on treatment with Lucas reagent at room temperature gives compound $B$. When compound $B$ is heated with alcoholic $KOH$,it gives isobutene. Compound $A$ and $B$ are respectively:

Which is most viscous?

Product $(P)$ is

$CH_3-CH(OH)-CH_3$ $\xrightarrow{PBr_3} X$ $\xrightarrow{Mg/\text{ether}} Y$ $\xrightarrow{H_2O/H^+} \text{The final product is}$

Write about the oxidation of alcohols.