Which of the following is known as a host bus adapter?

A host bus adapter (HBA) is a critical component within a computer system that facilitates communication between the operating system and the storage devices. It acts as the interface that connects the host system to the storage network or devices, such as hard drives or Solid State Drives (SSDs).

The option labeled HBA AC directly refers to a specific type of host bus adapter, indicating that it provides the functionality expected from an HBA. This connection is essential for efficient data transfer and communication, making it a core element in systems that require interaction with storage resources.

In contrast, while the USB controller is responsible for managing USB ports and devices connected to a computer, it does not fit the specific definition of a host bus adapter—its function is more limited to peripheral connections rather than direct connections to storage subsystems. The PCI bridge connects different parts of the motherboard and may manage multiple devices but is not inherently dedicated to storage interfaces like a typical HBA. Similarly, the display adapter is designed to render graphics and output video to a monitor, and thus does not serve the purpose of a host bus adapter in relation to storage communication.

Understanding the specific role of a host bus adapter helps clarify why HBA AC is the correct identification among the choices provided.