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

diff --git a/Doc/reference/import.rst b/Doc/reference/import.rst
index 7c4f275..d36d7d6 100644
--- a/Doc/reference/import.rst
+++ b/Doc/reference/import.rst
@@ -951,7 +951,7 @@
 :mod:`__main__` does not correspond directly with an importable module:
 
 - interactive prompt
-- -c switch
+- :option:`-c` option
 - running from stdin
 - running directly from a source or bytecode file