Strontium metal may be produced by electrolysing molten strontium bromide, $\text{SrBr}_2$, with the apparatus shown. Why is argon gas used to surround the cathode?
- AA thin film of a compound of strontium and argon forms on the surface protecting the freshly formed metal.
- BThe argon keeps the strontium molten.
- CThe argon stops the molten strontium rising too high in the tube.
- DWithout the argon, strontium oxide would form in the air.