Which of the following is NOT an operating system?

Correct option is D

The correct answer is (d) Intel.

Intel is a technology company that primarily manufactures microprocessors and semiconductors. It is not an operating system.
The other options are all operating systems:

• Mac (macOS) is an operating system developed by Apple.
• Linux is an open-source operating system.
• Windows is a popular operating system developed by Microsoft.

Information Booster

• Mac: macOS, used on Apple computers, is known for its smooth user experience and security features.
  
• Linux: A versatile and open-source operating system widely used for servers and in tech development.
  
• Windows: A dominant operating system used globally in personal computers and businesses.