Match DOS command names to their primary purposes: (A) DBLSPACE, (B) MEM, (C) SYS, (D) DELTREE — choose the correct mapping for disk compression, memory display, DOS system transfer, and recursive directory deletion.

Introduction / Context:
Legacy DOS commands still appear in certification exams and interviews because they illustrate core OS concepts: storage, memory, bootstrapping, and file-system operations. Correctly mapping these commands helps solidify command-line literacy.

Given Data / Assumptions:

• DBLSPACE: double-space compression utility for drives/files.
• MEM: reports used/free memory.
• SYS: transfers DOS system files to a disk (makes it bootable).
• DELTREE: deletes a directory and its subdirectories recursively.

Concept / Approach:
Recall canonical DOS usage: DBLSPACE /DRVSPACE for compression; MEM /C /P for memory; SYS A: to make a system disk; DELTREE C:\TEMP to remove a tree.

Step-by-Step Solution:

Verification / Alternative check:
Help outputs (e.g., 'MEM /?' or DOS manuals) corroborate each mapping and the typical switches used with each utility.

Why Other Options Are Wrong:

• A-4, B-3, C-2, D-1: Swaps MEM and SYS roles.
• A-2, B-3, C-4, D-1: Assigns compression to MEM; incorrect.
• A-1, B-2, C-3, D-4: Misplaces DBLSPACE and DELTREE functions.

Common Pitfalls:

• Confusing DBLSPACE (older) with DRVSPACE (later).
• Forgetting that DELTREE is dangerous and permanent.

Final Answer:
A-4, B-2, C-3, D-1