gnus-subscribe-options-newsgroup-method

gnus-subscribe-options-newsgroup-method is a variable defined in `gnus-start.el'.
Its value is

gnus-subscribe-alphabetically

Documentation:
*Function(s) called to subscribe newsgroups mentioned on "options -n" lines.
If, for instance, you want to subscribe to all newsgroups in the
"no" and "alt" hierarchies, you'd put the following in your
.newsrc file:

options -n no.all alt.all

Gnus will then subscribe all new newsgroups in these hierarchies
with the subscription method in this variable.

You can customize this variable.