The diagram shows a simplified schematic of part of the electricity distribution network in the UK.

The mains electricity supplied to UK homes is an alternating current (a.c.) supply.
What is the frequency of this supply?
0.5 Hz0.5\text{ Hz}0.5 Hz
50 Hz50\text{ Hz}50 Hz
230 Hz230\text{ Hz}230 Hz
320 Hz320\text{ Hz}320 Hz