To remove last traces of water from alcohol,the metal used is

Consider the following reaction:
$CH_3CH_2OH$ $\xrightarrow{PBr_3} X$ $\xrightarrow{alc. KOH} Y$ $\xrightarrow[(ii) H_2O, \text{heat}]{(i) H_2SO_4, \text{room temperature}} Z$
The product $Z$ is

In the reaction sequence:
$\text{Ethanol}$ $\xrightarrow{PCl_5} X$ $\xrightarrow{\text{alc. } KOH} Y$ $\xrightarrow[H_2O, \Delta]{H_2SO_4, \text{room temp.}} Z$
The product $Z$ is:

In glycerol,which of the following is true regarding the $-OH$ groups?

$A$ on heating isomerizes to $B$. What is the structure of $B$?

The product formed when glycerol reacts with $PCl_5$ is -