Concept:The Start button is a standard part of the Windows desktop interface, located on the taskbar.Explanation:The taskbar is the horizontal bar usually at the bottom of the screen. It contains the Start button, open program buttons, and other shortcuts.The scroll bar is used for scrolling, the status bar shows information, and the system tray holds icons for background programs.Therefore, the Start button is found on the task bar.Answer:A. task bar.