A basic service set (BSS) is a group of wireless devices that share the same service set identifier (SSID) and communicate with each other through a single access point (AP). A BSS is also known as an infrastructure mode network1.
An extended service set (ESS) is a group of two or more BSSs that are connected by a distribution system (DS), such as a switch or a router. An ESS allows wireless devices to roam between different APs and maintain network connectivity. An ESS is also known as a wireless LAN (WLAN)2.
An independent basic service set (IBSS) is a group of wireless devices that communicate with each other directly without using an AP or a DS. An IBSS is also known as an ad hoc network or a peer-to-peer network3.
MU-MIMO (Multi-User Multiple-Input Multiple-Output) is a technology that allows an AP to transmit data to multiple wireless devices simultaneously using multiple antennas and spatial streams. MU-MIMO can improve the network efficiency and performance by reducing the waiting time and increasing the throughput4.
The scenario described in the question is an example of an IBSS, as the two laptops are connected directly to each other using 802.11ac without an AP. Therefore, the correct answer is C.
Reference:
1: BSS
2: ESS
3: IBSS
4: MU-MIMO