Iodoform can be obtained on warming $NaOH$ and iodine with

Give the structures of $A$,$B$,and $C$ in the following reaction:
$CH_3-CH_2-CH(OH)-CH_3$ $\xrightarrow{Cu, 520 \ K} (A)$ $\xrightarrow{C_2H_5MgBr} (B)$ $\xrightarrow{H_3O^+} (C)$

Product $(B)$ of the above reaction is

The reaction of ethylene glycol with $PI_3$ gives:

Identify $P_3$ in the following reaction sequence:

The correct order of dehydration of alcohols is