Select the correct passive form of the given sentence.
The groundsman switched on the lights of the football stadium before it began to grow dark.
1
The lights of the football stadium were only switched on before it began to grow dark.
2
The lights of the football stadium are being switched on before it began to grow dark.
3
The lights of the football stadium were being switched on by the groundsman before it began to grow dark.
4
The lights of the football stadium were switched on by the groundsman before it began to grow dark.