Solution:

The layers of the MS-DOS operating system from the innermost to the outermost are:

1. (A) ROM BIOS Device drivers – These are the lowest-level drivers stored in ROM that directly interact with the hardware.
2. (C) MS-DOS Device Drivers – These drivers are loaded by MS-DOS during boot and extend the hardware control provided by BIOS.
3. (B) Resident System Program – The core of MS-DOS (command interpreter and kernel) which manages the system operations.
4. (D) Application Program – User-level programs that run on top of MS-DOS, depending on the lower layers.

Therefore, the correct sequence is:

✅ (A) → (C) → (B) → (D)