The correct answer is: A. Alt
The Alt key is a modifier key on most computer keyboards. It is used to access alternative commands or functions, often in combination with other keys. For example, pressing Alt+F4 closes the current window, and pressing Alt+Tab switches between open windows.
To see the underlined hidden access key, you can do so, by pressing the Alt key. When you press the Alt key, the underlined letters on the keyboard will become visible. These letters are the access keys for various commands and functions. For example, the access key for the File menu is F, so pressing Alt+F will open the File menu.
The other options are incorrect because they do not access the underlined hidden access key. The Ctrl key is used to access shortcut keys, the Shift key is used to type uppercase letters and symbols, and the Enter key is used to submit forms and commands.