a window frame will expand to fill the entire desktop when you

a.double-click the taskbar
b.click the title button marked with a single square
c.click the titlebar marked with two overlapping squares

my answer is c

can someone please help me

I disagree.

You're guessing.

What are you using for instructional materials? A textbook? Trial and error? What?

To confirm whether your answer is correct, let's go through each option and explain how to expand a window frame to fill the entire desktop:

a. Double-click the taskbar: Double-clicking the taskbar usually does not expand a window frame to fill the entire desktop. Instead, it typically minimizes or maximizes the window, depending on its current state.

b. Click the title button marked with a single square: This option is quite common on many windows, specifically the maximization button. When you click the title button marked with a single square, the window will be maximized, meaning it will expand to fill the entire desktop.

c. Click the title bar marked with two overlapping squares: This option usually represents the "restore" or "resize" button. Clicking it does not make the window fill the entire desktop. Instead, it typically restores the window to its previous size or allows you to manually resize it by clicking and dragging the edges.

Based on these explanations, your answer (c) is incorrect. The correct answer is (b) - clicking the title button marked with a single square will expand the window frame to fill the entire desktop.