Leonidas wants to use a low-power, personal area network (PAN) wireless protocol for a device he is designing. Which of the following wireless protocols is best suited to creating small, low-power devices that can connect to each other at relatively short distances across buildings or rooms?

Zigbee is designed for this type of low-power, Internet of Things network, and would be the best option for Leonidas. Some versions of Bluetooth are designed to operate in low-power mode as well, but Bluetooth isn't in this list of answers. Wi-Fi requires more power, NFC is very short range and would not work across a building or room, and infrared requires line of sight and is rarely used for that reason.