Field-replaceable units (FRUs): which of the following is best classified as an input/output device?

Introduction / Context:
FRUs are components designed for quick replacement. Categorizing them by function helps in troubleshooting and inventory planning. The question asks which listed FRU is explicitly an I/O device—something that interfaces the system bus to external or peripheral buses.

Given Data / Assumptions:

• Video board primarily outputs display signals.
• SCSI host adapter connects system to storage/peripheral SCSI bus (bidirectional).
• CPU is the central processor, not an I/O controller.

Concept / Approach:
An I/O device mediates data transfer between the CPU/memory subsystem and external devices. A SCSI host adapter provides this interface, handling command, data, and status phases in both directions. A video board primarily outputs frames (with limited input such as EDID reads, but it is not generally termed an I/O controller). The CPU executes instructions and coordinates I/O but is not itself an I/O device.

Step-by-Step Solution:

Verification / Alternative check:
System device manager lists the SCSI adapter under storage controllers (I/O), not under processors or display adapters.

Why Other Options Are Wrong:

• Video board: Primarily output; not a general I/O bus controller.
• CPU: Core compute element; not categorized as an I/O device.
• All of the above / None: Over-broad or incorrect.

Common Pitfalls:
Assuming any card is “I/O.” Many GPUs are output-only devices from a classification standpoint.

Final Answer:
SCSI host adapter