Explanation:

Correct answer: (C) MS-DOS and (D) LINUX
But if you can choose only one, then:

Best answer: (C) MS-DOS

Explanation:

(A) Mac OS X:
Primarily uses a Graphical User Interface (GUI), though it has a terminal with command-line capabilities (Unix-based).

(B) Windows 7:
Also primarily GUI-based, with optional access to Command Prompt.

(C) MS-DOS (Microsoft Disk Operating System):
A pure Command Line Interface (CLI) system — no GUI at all.

(D) LINUX:
Can run both CLI (via terminal/shell) and GUI (via desktop environments like GNOME, KDE). So, it supports CLI but is not CLI-only.

So:

• If the question expects only CLI-only OS, then (C) MS-DOS is the best choice.
• If multiple answers are allowed, then (C) and (D) are both correct.