``a lot'' of blank lines), and @kbd{C-u C-k} (kill four lines).
Some commands care whether there is an argument, but ignore its
-value. For example, the command @kbd{M-q} (@code{fill-paragraph-or-region})
+value. For example, the command @kbd{M-q} (@code{fill-paragraph})
fills text; with an argument, it justifies the text as well.
(@xref{Filling}, for more information on @kbd{M-q}.) Plain @kbd{C-u}
is a handy way of providing an argument for such commands.