Introduction:
A wireless network interface controller (WNIC) is a hardware device that enables a computer or other device to connect to a wireless network. It is responsible for transmitting and receiving data over the wireless network. A WNIC can operate in different modes depending on the network requirements.

Infrastructure Mode:
Infrastructure mode is the most common mode of operation for wireless networks. In this mode, the WNIC connects to a wireless access point (AP) or router that acts as a central hub for the network. The AP is responsible for managing the network and providing connectivity to devices. The WNIC communicates with the AP to access the network resources and transmit/receive data. This mode is suitable for scenarios where multiple devices need to connect to a central network infrastructure, such as in homes, offices, or public places.

Ad-hoc Mode:
Ad-hoc mode, also known as peer-to-peer mode, allows devices to connect directly to each other without the need for a central AP or router. In this mode, each device acts as a node and communicates directly with other devices within range. Ad-hoc networks are useful in situations where a central infrastructure is not available or practical, such as in temporary or remote locations. Devices in an ad-hoc network can share resources, such as files or printers, without relying on a central server.

Both (a) and (b):
A WNIC can work in both infrastructure mode and ad-hoc mode. It is designed to support both modes of operation, allowing flexibility in connecting to different types of wireless networks. This means that a WNIC can connect to a wireless network with a central AP in infrastructure mode, or it can directly connect to other devices in ad-hoc mode. The choice of mode depends on the network requirements and the available infrastructure.

Conclusion:
In summary, a wireless network interface controller (WNIC) can operate in both infrastructure mode and ad-hoc mode. Infrastructure mode is used when connecting to a network with a central AP or router, while ad-hoc mode is used for direct device-to-device communication. The ability to operate in both modes provides flexibility and compatibility with different network setups.