John is conducting an investigation as to why a network server has failed. During the investigation he has discovered the following facts:

The cause of the failure was an electrical overload, which disabled the computer

There wasn't an adequate surge protector connected to the server

There is an adequate uninterruptable power supply connected to the server

It is known that the power within the building is prone to power spikes, surges, brownouts, and blackouts

Which of these would be considered a control?

$3$

$1$

$4$

$2$