Which one of the following electrolytes is used in Down’s process of extracting sodium metal? 

You must be able to recollect the procedures used to extract the different metals in order to respond to this question. The electrochemical extraction technique known as Down's procedure is used to prepare sodium metal
The Down's method is an extraction technique built on the electrolysis tenet. It is a frequently utilised metal for the large-scale commercial extraction of metallic sodium. Molten sodium chloride is subjected to electrolysis in this process.

The process-related reaction occurring at the anode is $2C{l}^{-}\to C{l}_2+2e^{-}$
The process-related reaction occurring at the cathode is $2N{a}^{+}+2e^{-}\to 2Na$
The general cell response is provided as $2{\mathrm{Na}}^{+}+2{\mathrm{Cl}}^{-}\to 2\mathrm{Na}+{\mathrm{Cl}}_2$

The process is also complicated by the fact that sodium chloride is an ionic molecule with a relatively high melting point. It melts at a temperature of around 1074K, which is extremely challenging to reach. In order to lower the melting point, potassium chloride and potassium fluoride are consequently added. Additionally, they improve the electrolytic process' electrical conductivity, which increases its viability.

Hence, the correct answer is option A.