Which of the following terms is used to describe the process of issuing a public invitation for people to try out for roles in films rather than casting directors contacting actors' agents about available roles?

Open casting

Explanation:

An open casting call (or an open audition) is an invitation extended by casting directors to people, regardless of previous status as actors, to try out for available roles in a film.

This is opposed to a situation where the casting directors call agents of established actors to alert them and negotiate over available roles.

In an open casting call, due to the usually high number of people who turn up, a lot of invitees may be screened out, before they even get the chance to audition for the role.