Which of the following is used as a catalyst for preparing Grignard reagent?

$2-$methylpropane can be prepared by the Wurtz reaction. The haloalkanes taken along with metallic sodium and dry ether are:

By which reaction is Freon-$12$ $(CCl_2F_2)$ prepared from $CCl_4$?

Ethanol is converted into ethyl chloride by reacting with

To obtain a Grignard reagent,magnesium is reacted with......?

The products $A$ and $B$ obtained in the following reactions,respectively,are
$3 ROH + PCl_3 \rightarrow 3 RCl + A$
$ROH + PCl_5 \rightarrow RCl + HCl + B$