Fix plural.

Misc/Porting

@@ -31,7 +31,7 @@ target platform.  Forget about the posix module for now -- simply take
 it out of the config.c file.
 
 Bang on it until you get a >>> prompt.  (You may have to disable the
-importing of "site.py" by passing the -S options.)
+importing of "site.py" by passing the -S option.)
 
 Then bang on it until it executes very simple Python statements.