To enable a PC to emulate a graphics terminal (e.g., Tektronix-style or ANSI graphics), you primarily need appropriate terminal emulation software that speaks the terminal's control protocols; assume a standard graphics adapter is already present.

Introduction / Context:
Personal computers can mimic (emulate) legacy graphics terminals used by plotters, CAD workstations, and mainframes. Emulation requires the PC to interpret the terminal's escape codes and drawing commands, then render equivalent graphics locally. The key enabler is the terminal emulation software that implements the correct protocol and command set for the target terminal type.

Given Data / Assumptions:

• The PC already has a standard graphics adapter suitable for basic rendering.
• We want to emulate the behavior of a graphics terminal over serial or network connections.
• Only one choice should be identified as the primary requirement.

Concept / Approach:
Terminal emulation is fundamentally a software problem: parse incoming control sequences, maintain a local screen/graphics buffer, and draw lines, points, and text. The software maps terminal-specific drawing primitives to the PC’s graphics APIs. While better graphics hardware can improve performance or resolution, hardware alone cannot interpret terminal protocols without software. Likewise, printers or color monitors are peripheral to emulation and not required to implement terminal behavior.

Step-by-Step Solution:
Identify what a graphics terminal does: receive commands and render graphics.Determine what lets a PC understand those commands: terminal emulation software.Note that standard PC graphics hardware is assumed; extra devices are not strictly required.Select the option that provides the necessary interpretation layer: software.

Verification / Alternative check:
Well-known terminal emulators (e.g., Tektronix/VT emulators) run purely as software on PCs, using existing graphics adapters to display lines, vectors, and plots. This confirms that software is the essential enabler for emulation.

Why Other Options Are Wrong:
A laser printer: output device, unrelated to real-time terminal emulation.A color monitor: helpful but not required; monochrome can still emulate.A graphics board: most PCs already have one; without software, emulation cannot occur.None of the above: incorrect because software is required.

Common Pitfalls:
Confusing display capability with protocol emulation; overlooking serial/network configuration and baud/flow control; assuming color is necessary when many classic terminals were monochrome. Always ensure the emulator matches the exact terminal type (escape codes, coordinate system, vector primitives).

Final Answer:
Software