What does Control-_ do in MySQL input editor?

In the MySQL input editor, pressing Control- undoes the last change made to the text.
Option A, copies to clipboard, is incorrect because Control- does not copy text to the clipboard.
Option B, pastes from clipboard, is incorrect because Control-_ does not paste text from the clipboard.
Option D, deletes the current line, is incorrect because Control-_ does not delete the current line in the MySQL input editor; instead, it undoes the last change made to the text.