The tkinter.messagebox.askquestion() function is designed to present a user with a dialog box containing a specific message and two buttons: "Yes" and "No". According to the official Python documentation for the tkinter library, the function's return value is directly tied to the button the user selects. If the user clicks the "Yes" button, the function returns the string 'yes'. If the user clicks the "No" button, it returns the string 'no'. This is distinct from other dialog functions like askyesno, which returns boolean values.

A. "accept:" and "cancel'': These are not valid return values for any standard tkinter.messagebox function. The askokcancel function returns boolean True or False.

B. l and o: These are not valid return values. The function returns the specific strings 'yes' or 'no', not integers (like 1 and 0) or single characters.

D. True and False: These boolean values are returned by the askyesno() and askokcancel() functions, but not by askquestion().

1. Python Software Foundation. Python 3.12.3 Documentation, "tkinter.messagebox — Tkinter Dialogs". Accessed May 2024. https://docs.python.org/3/library/tkinter.messagebox.html.

Reference Specifics: In the section describing the available functions, the entry for tkinter.messagebox.askquestion(title=None, message=None, options) explicitly states: "Ask a question. Return 'yes' or 'no'."

2. Tcl/Tk Documentation. Tcl/Tk 8.6 Manual, "tkmessageBox - pops up a message window and waits for user response." Accessed May 2024. https://www.tcl.tk/man/tcl8.6/TkCmd/messageBox.htm.

Reference Specifics: Under the -type option, the documentation for question specifies that the dialog box contains "Yes" and "No" buttons. The documentation states that the command returns the symbolic name of the button selected by the user, which are yes and no.

3. Lutz, M. (2013). Programming Python, 5th Edition. O'Reilly Media. (Note: While a commercial book, it is widely used as a reference in academic settings and is considered an authoritative text on the language).

Reference Specifics: Chapter 8, "A Tkinter Tour, Part 1," in the section on standard dialogs, explains that askquestion returns the strings 'yes' or 'no', contrasting it with askyesno which returns boolean True or False.