Mark -c and -O as command line options in reStructuredText. (GH-10103)

diff --git a/Doc/reference/executionmodel.rst b/Doc/reference/executionmodel.rst
index 5c83181..1a69e97 100644
--- a/Doc/reference/executionmodel.rst
+++ b/Doc/reference/executionmodel.rst
@@ -22,7 +22,7 @@
 Each command typed interactively is a block.  A script file (a file given as
 standard input to the interpreter or specified as a command line argument to the
 interpreter) is a code block.  A script command (a command specified on the
-interpreter command line with the '**-c**' option) is a code block.  The string
+interpreter command line with the :option:`-c` option) is a code block.  The string
 argument passed to the built-in functions :func:`eval` and :func:`exec` is a
 code block.