The correct answer is: A. Lightning arresters.
Lightning arresters are devices that are used to protect electrical equipment from damage caused by lightning strikes. They are typically installed on the transmission line, and they work by diverting the high voltage of a lightning strike to the ground.
Relays are devices that are used to control the flow of electricity in a circuit. They are typically installed in switchgear, and they work by opening and closing circuits based on certain conditions.
Step-down transformers are devices that are used to reduce the voltage of electricity. They are typically installed at the end of a transmission line, and they work by converting the high voltage of the transmission line to a lower voltage that can be used by homes and businesses.
Switchgear is a system of electrical equipment that is used to control and protect electrical circuits. It typically includes circuit breakers, fuses, and other devices that are used to isolate and disconnect electrical circuits in the event of a fault.
Lightning arresters are the first devices to receive voltage surge first travelling on the transmission line because they are installed on the transmission line and they are designed to divert the high voltage of a lightning strike to the ground.