When executed from a bootable hard drive, which command correctly makes an already formatted floppy disk in drive A: bootable by transferring DOS system files and a boot sector?

Introduction / Context:
To create a bootable floppy from an already formatted disk, you must transfer the DOS system files and write a compatible boot sector. Copying visible files alone is insufficient because the boot code lives in the boot sector and some system files may be hidden or require placement rules enforced by the utility designed for this purpose.

Given Data / Assumptions:

• The disk in A: is already formatted.
• You are running from a working, bootable hard drive with DOS installed.
• Your goal is to make A: independently bootable.

Concept / Approach:
The SYS command copies the necessary system files (for example, IO.SYS, MSDOS.SYS, COMMAND.COM depending on DOS version) and updates the boot sector so that the machine can boot directly from A:. While FORMAT A: /S could accomplish both formatting and system transfer in one step, the prompt here specifies that the floppy is already formatted, so SYS A: is the most direct and correct choice.

Step-by-Step Solution:

Verification / Alternative check:
List the floppy contents and note that essential system files are now present (some may be hidden). Attempting to boot validates that the boot sector and files are correct.

Why Other Options Are Wrong:

• XCOPY C:\DOS\.* A:\: Copies many files but does not write the boot sector and may omit hidden system constraints.
• COPY C:\DOS\COMMAND.COM A:\: Copies only the command interpreter, not the full boot chain.
• ATTRIB C:\*.SYS A:\: Changes attributes; it does not create a bootable disk.
• None of the above: Incorrect because SYS A: is exactly the right tool.

Common Pitfalls:
Assuming that copying visible files makes media bootable, forgetting that some DOS versions place strict requirements on system file placement, and running SYS on an unformatted disk.

Final Answer:
SYS A: