What is an icon?

1) an element of the start menu
2) a link to online and support
3) an image on the background of the desktop
4) a small picture that represents a program or tool

The answer to the given question is the option "4".

Explanation:

Icon is a small picture that helps the user to recognize a thing more easily. In computer science, an icon is a small picture or symbol that is used to provide a graphical description of the software program on a computer screen. In this question all other option is not correct that can be described as:  

The start menu is a button on the computer. In this button, there are many options or sub buttons. like, documents, pictures, help, and support, control panel, etc. So, it is not an icon.  

In the start menu, there is an option of the help and support so it is not an icon.

The background image is also known as wallpaper. So it is not an icon. That's why the answer to this question is the option "4".