Wording: "first module" -> "top level module"

README.md

@@ -10616,7 +10616,7 @@ How about `pub` for a struct, enum, trait, or module? `pub` works like this for
 
 - `pub` for a struct: it makes the struct public, but the items are not public. To make an item public, you have to write `pub` for each one too.
 - `pub` for an enum or trait: everything becomes public. This makes sense because traits are about giving the same behaviour to something. And enums are about choosing between items, and you need to see them all to choose them.
-- `pub` for a module: the first module will be `pub` because if it isn't pub then nobody can touch anything in it at all. But modules inside modules need `pub` to be public.
+- `pub` for a module: a top level module will be `pub` because if it isn't pub then nobody can touch anything in it at all. But modules inside modules need `pub` to be public.
 
 So let's put a struct named `Billy` inside `print_things`. This struct will be almost all public, but not quite. The struct is public so it will say `pub struct Billy`. Inside it will have a `name` and `times_to_print`. `name` will not be public, because we only want the user to create structs named `"Billy".to_string()`. But the user can select the number of times to print, so that will be public. It looks like this: