An application communicates with the user through . . . . . . . .

DialogBox
AlertBox
MessageBox
AlertDialog

The correct answer is: D. AlertDialog

An AlertDialog is a dialog box that displays a message and an optional set of buttons. The user can click on one of the buttons to take an action, such as dismissing the dialog box or performing a task.

A DialogBox is a modal dialog box that displays a message and an optional set of buttons. The user must click on one of the buttons before the application can continue.

A MessageBox is a non-modal dialog box that displays a message. The user can click on any part of the screen to dismiss the message box.

A Dialog is a general term for a window that displays information to the user. It can be a modal dialog box, a non-modal dialog box, or an AlertDialog.