What is meant when we say that a network of devices is operating in "infrastructure mode"?

Group of answer choices

All network equipment, except the mobile devices, must be racked in a temperature$-$controlled and power$-$smoothed building.

Network devices can communicate directly with each other, with no need for messages to be relayed through a base station. The devices are the "infrastructure".

The mobile device is operating in a reduced power mode, forcing the network base station and routers to take on additional functionality that would normally be done by the mobile.

Devices communicate with each other and to the larger outside world via a base station $($also known as an access point$).$