Enforcement Officer / Accounts Officer (EO/AO) 2020 recruitment test, advertisement 421. Transcribed from the Commission's own booklet (series A, NMJX-U-GTA); answer as per the official UPSC final answer key. This question is in Part B. Answer last reviewed 24 August 2026.

Which one of the following is not a web browser ?

(a)Internet Explorer
(b)Firefox
(c)Fedora
(d)Google Chrome

Answer

Why

Correct — C, (c) Fedora. The word 'not' is printed in bold italic on the booklet, so the question wants the odd one out: three of the four names are web browsers and one is not. Fedora is a Linux distribution — an operating system, complete with a kernel, a desktop environment and a package manager — developed by the Fedora Project, begun in 2003 as a continuation of the Red Hat Linux project, and now the upstream source for CentOS Stream and Red Hat Enterprise Linux. A browser is an application that runs on top of an operating system; Fedora is the layer underneath, and in fact a Fedora desktop typically ships with Firefox installed on it, which is part of why the name sits comfortably in a list of browsers to anyone who has not met it. Internet Explorer, Firefox and Google Chrome are all programs for fetching and rendering web pages. Fedora is the environment in which such a program is run.

Why the others are wrong

(a)Internet Explorer — Internet Explorer is a web browser — Microsoft's, first released in 1995 and bundled with Windows for many years, which is how it came to dominate the early web. Microsoft replaced it as the default browser in Windows 10 with Edge in 2015, and support for Internet Explorer ended in 2022, but a browser it certainly was, so it cannot answer a question asking which name is NOT one. Being obsolete is not the same as being the wrong kind of thing.
(b)Firefox — Firefox is a web browser developed by the Mozilla Foundation, and it is free and open-source software. It is the browser most often shipped as the default on Linux desktops, Fedora's included, which is exactly the association that makes this item work as a trap in the other direction: a candidate who has seen the two names together may conclude that both are browsers or that both are operating systems. Firefox is the browser; Fedora is the system it runs on.
(d)Google Chrome — Google Chrome is a web browser, released by Google in 2008 and since the most widely used browser on both desktop and mobile. Note that Chrome the browser is a different thing from Chrome OS, the operating system Google builds around it — that pair is worth keeping straight, because a question can be built on it in the same way this one is built on Fedora. Here the option names the browser, so it is a correct member of the list and not the exception.

Concept

The distinction the question turns on is between system software and application software. An operating system is system software: it manages the hardware, allocates memory and processor time, handles files and devices, and provides the environment in which everything else runs. Windows, macOS, Android, iOS and the many Linux distributions — Fedora, Ubuntu, Debian, Red Hat Enterprise Linux, Linux Mint — are operating systems. A web browser is application software: a program that runs on an operating system, sends requests over HTTP or HTTPS to a web server, receives HTML, CSS, JavaScript and images in reply, and renders them into a page. Internet Explorer, Edge, Firefox, Chrome, Safari and Opera are browsers. 'Linux distribution' means the Linux kernel packaged together with system utilities, a desktop and a body of applications, which is why different distributions of the same kernel feel like different systems. The confusion this question exploits is a real one: browser and system names circulate in the same conversations, and several companies supply both. Google makes Chrome the browser and Chrome OS the operating system; Microsoft makes Edge and Windows; Apple makes Safari and macOS; Red Hat's ecosystem produced Fedora, and Fedora machines run Firefox.

This is a classification item asked as a negative, and it is a common shape in the EO/AO computer block: three members of a category and one intruder from a neighbouring category. The reliable method is to name the category the three share before deciding about the fourth, because the intruder is always plausible in context — nobody sets a question with an obviously absurd option. The habit worth building for this whole block is to keep two lists in memory, one of operating systems and one of applications, and to notice which companies supply both, since that is where the traps are made.

Key facts

Fedora Linux is a Linux distribution developed by the Fedora Project, begun in 2003 as a continuation of the Red Hat Linux project.
Fedora is now the upstream source for CentOS Stream and Red Hat Enterprise Linux, and releases roughly every six months.
System software manages the machine; application software does the user's work. An operating system is the first, a browser the second.
Internet Explorer is Microsoft's browser, first released in 1995; Edge replaced it as the Windows default in 2015 and its support ended in 2022.
Firefox is developed by the Mozilla Foundation and is free and open-source software.
Google Chrome was released in 2008 and is distinct from Chrome OS, which is an operating system.
Other Linux distributions likely to appear as intruders in such a list: Ubuntu, Debian, Linux Mint, Red Hat Enterprise Linux.
Other browsers likely to appear: Safari (Apple), Opera, Microsoft Edge.

System software against application software

Fedora→A Linux distribution — the Linux kernel packaged together with system utilities, a desktop environment and a body of applications. Developed by the Fedora Project from 2003 as a continuation of the Red Hat Linux project, and now the upstream source for CentOS Stream and Red Hat Enterprise Linux. It is the layer a browser runs ON, not a browser.

Internet Explorer→Microsoft’s browser, first released in 1995 and bundled with Windows for many years, which is how it came to dominate the early web. Edge replaced it as the Windows default in 2015 and its support ended in 2022 — but being obsolete is not the same as not being a browser.

Firefox→A browser developed by the Mozilla Foundation, free and open-source. It is the browser most often shipped as the default on Linux desktops, Fedora’s included, and that association is exactly what makes this item work as a trap in both directions.

Google Chrome→Released by Google in 2008 and since the most widely used browser on both desktop and mobile. Keep it apart from Chrome OS, the operating system Google builds around it — a question can be made out of that pair in the same way this one is made out of Fedora.

What separates the two classes→An operating system manages the hardware, allocates memory and processor time, and handles files and devices. A browser is a program that runs on top of it, sends requests over HTTP or HTTPS to a web server, and renders the HTML, CSS, JavaScript and images that come back.

Other names likely to appear in such a list→Operating systems — Ubuntu, Debian, Linux Mint, Red Hat Enterprise Linux, Windows, macOS, Android, iOS. Browsers — Safari, Opera, Microsoft Edge. Several companies supply both: Microsoft makes Edge and Windows, Apple makes Safari and macOS.

Study next

System software versus application software, with utilities as a third categoryOperating system functions: process, memory, file and device managementOpen-source licensing and the free software movement, and why Linux comes in distributionsHow the web works: client, server, HTTP and HTTPS, URL, IP address and DNSSearch engines versus browsers versus web portals — a distinction the same question family exploits

Common traps

Missing the bold-italic 'not' and picking the most familiar browser on the list.
Confusing a browser with the operating system that ships it — Fedora ships Firefox, which makes the two names travel together.
Confusing Chrome the browser with Chrome OS the operating system, or Edge with Windows.
Assuming that a discontinued product is the odd one out. Internet Explorer is obsolete and still a browser.
Confusing a browser with a search engine: Google is a search engine, Google Chrome is a browser, and questions are built on the difference.

Odd-one-out items are the standard form for this block on EPFO EO/AO papers, and the categories rotate: browsers, operating systems, programming languages, input devices, file formats, output devices. The options are one or two words long. Expect the intruder to be a real product from an adjacent category, never a nonsense name, so recognising the name is never enough — the category has to be recalled as well.

Related PYQs

EPFO_EOAO_2020_Q27Open & attempt →

Which one of the following basic operations for converting raw input data into useful information is not performed by all computers ?

(a) Inputting
(b) Storing
(c) Switching
(d) Outputting

Answer(c) Switching

The other negative identification item in this computer block, built the same way — three genuine members of a category and one intruder, with the negation printed in bold italic.

Practice

practice — not a real PYQ
Which one of the following is an operating system ?
- (a)Safari
- (b)Opera
- (c)Ubuntu
- (d)Microsoft Edge
Answer(c) Ubuntu
practice — not a real PYQ
The Firefox web browser is developed by which one of the following ?
- (a)Google
- (b)Mozilla Foundation
- (c)Red Hat
- (d)Microsoft
Answer(b) Mozilla Foundation

Why