MS-Excel, the popular spreadsheet program from Microsoft, was originally developed and is primarily designed to run on which family of operating systems?

Introduction / Context:
MS-Excel is one of the most widely used spreadsheet applications in the world. Knowing which operating system family it is primarily associated with is a common question in computer awareness exams. While there have been versions for other platforms, Excel became famous and heavily used as part of the Microsoft Office suite on Windows.

Given Data / Assumptions:

• The question asks which operating system family MS-Excel is based on or primarily designed for.
• Options include OS/2, UNIX, Windows, DOS and classic Mac OS.
• We assume mainstream exams that emphasise Excel as part of Microsoft Office on Windows PCs.

Concept / Approach:
Excel is a Microsoft product that became ubiquitous on Windows operating systems. Modern versions of Excel are distributed as part of Microsoft Office for Windows. Although early spreadsheet programs like Multiplan and early Excel versions existed for Mac and other systems, basic computer awareness books highlight Excel as a Windows based spreadsheet package. Therefore, the most accurate answer in an exam context is Microsoft Windows operating systems.

Step-by-Step Solution:
Step 1: Recognise that Microsoft develops both the Windows operating system and the Office suite that includes Excel. Step 2: Most users encounter Excel on Windows PCs in homes, offices and computer labs. Step 3: Option c, Microsoft Windows operating systems, directly names this platform. Step 4: OS/2, developed by IBM and Microsoft initially, is a separate operating system that never became the main platform for Excel in education or business. Step 5: UNIX is a family of operating systems used in servers and technical computing; Excel is not typically presented as a native UNIX program in basic computer courses. Step 6: DOS is a command line environment that predates graphical Office suites; Excel as students know it is a graphical Windows application, not a pure DOS program. Step 7: Classic Mac OS had a version of Excel, but exam questions aimed at general computer awareness usually emphasise Excel as a Windows based spreadsheet. Step 8: Therefore, the best educationally correct answer is that Excel is based on and primarily designed for Windows.

Verification / Alternative check:
Microsoft's official product pages list Excel as part of Microsoft Office for Windows and Microsoft 365. Installation instructions and screenshots almost always show the Windows environment. Although there are Mac and web versions, training material in many computer fundamentals courses consistently describes Excel within the context of Windows features such as the taskbar and ribbon interface. This supports choosing Windows as the primary platform in exam style questions.

Why Other Options Are Wrong:
OS/2 and UNIX have their own sets of applications and do not serve as the main historical platforms for Excel in general education. DOS is text based and unsuitable for the modern graphical Excel interface. Classic Mac OS did host early versions of Excel, but in most exam curricula, Excel is introduced as the spreadsheet that comes with Microsoft Office for Windows. Hence, selecting these alternatives would not align with the dominant educational framing.

Common Pitfalls:
Students may overthink the question if they are aware that Microsoft has released Excel for multiple platforms. However, competitive exams usually focus on the most common association. To avoid confusion, remember that when someone mentions MS-Excel in standard computer literacy classes, they almost always mean the Windows version that is part of Microsoft Office.

Final Answer:
MS-Excel is primarily based on and designed for Microsoft Windows operating systems.