The question asks about the best wireless standard for a WLAN project that involves MU-MIMO and dual-band frequencies.
The answer is not A, because 802.11ac is a wireless standard that supports MU-MIMO, but only operates on the 5GHz frequency band, which does not meet the project requirement of compatibility with 2.4GHz clients.
The answer is not C, because 802.11g is a wireless standard that operates on the 2.4GHz frequency band, but does not support MU-MIMO, which is a key feature for improving connection performance in high-density areas.
The answer is not D, because 802.11n is a wireless standard that operates on both 2.4GHz and 5GHz frequency bands, but only supports SU-MIMO (Single-User Multiple-Input Multiple-Output), which is less efficient and scalable than MU-MIMO for multiple concurrent connections.
The answer is B, because 802.11ax is a wireless standard that supports MU-MIMO and operates on both 2.4GHz and 5GHz frequency bands, which meets the project requirements of compatibility and performance. 802.11ax is also known as Wi-Fi 6, and it offers higher data rates, lower latency, and better energy efficiency than previous wireless standards.
Reference:
1: CompTIA Network+ N10-008 Study Guide, Chapter 3: Network Components, Section 3.1: Network Devices, p. 121
2: CompTIA Network+ N10-008 Study Guide, Chapter 3: Network Components, Section 3.2: Wireless Technologies, p. 134
3: CompTIA Network+ N10-008 Study Guide, Chapter 3: Network Components, Section 3.2: Wireless Technologies, p. 136
4: CompTIA Network+ N10-008 Study Guide, Chapter 3: Network Components, Section 3.2: Wireless Technologies, p. 139