The correct answer is option 'B' - Tool bar.

A toolbar is a graphical interface element that provides quick access to commonly used commands and tools in a software application. It typically appears as a row or column of icons or buttons located just below the menu bar or above the main content area of an application window.

Here's an explanation of why a toolbar can be used for quick access to commonly used commands and tools:

1. Definition and Purpose of a Toolbar:
- A toolbar is a set of buttons or icons that represent various functions or tools within an application.
- It is designed to provide easy and quick access to frequently used commands and tools, enhancing the user's productivity and efficiency.
- Toolbars are commonly found in applications like word processors, graphic design software, web browsers, and many other software programs.

2. Placement and Visibility:
- Toolbars are usually positioned below the menu bar or at the top of the application window, making them easily accessible and visible to the user.
- The toolbar remains visible even when other windows or dialog boxes are opened, ensuring continuous access to the commonly used commands and tools.

3. Icon-Based Representation:
- Toolbars use icons or small graphical images to represent different functions or tools.
- Icons are visually appealing and can be easily recognized by users, allowing them to quickly identify and select the desired command or tool.

4. Quick Access to Commands and Tools:
- By clicking on an icon or button in the toolbar, users can instantly access a specific command or tool without the need to navigate through menus or search for options.
- This saves time and effort, especially for frequently used functions, as they are readily available at the user's fingertips.

5. Customization:
- Toolbars are often customizable, allowing users to add or remove buttons based on their preferences and requirements.
- Users can tailor the toolbar to include only the commands and tools they frequently use, further enhancing their efficiency and workflow.

In conclusion, a toolbar is a user-friendly interface element that provides quick access to commonly used commands and tools in an application. Its placement, visual representation, and customization options make it an efficient and convenient way for users to interact with software programs.