802.11ac is a Wi-Fi standard that primarily operates in the 5GHz band and is known for higher throughput and improved performance compared with older 2.4GHz-focused standards. In CompTIA A+ Core 1 networking objectives, you are expected to recognize which IEEE 802.11 standards map to which frequency bands and the typical trade-offs. The 5GHz band generally provides more available non-overlapping channels and less interference from common household devices (like microwaves and many Bluetooth peripherals), which can improve real-world performance. While 5GHz typically has shorter range and weaker wall penetration than 2.4GHz, it often delivers better speeds in the same-room or nearby-room scenarios, which aligns with how 802.11ac is commonly deployed.

Bluetooth primarily uses the 2.4GHz ISM band and is designed for short-range personal area networking rather than high-speed WLAN connections. NFC operates at 13.56MHz for very short-range tap-based communications. RFID can operate at several bands (low frequency, high frequency, ultra-high frequency) depending on the use case, but it is not a Wi-Fi networking standard and does not “primarily” operate at 5GHz. Therefore, the correct answer is 802.11ac.