Any party may serve written interrogatories upon any other party, subject to the limits of Rule 26(c)(5). A party must disclose to the other parties the information, documents and witnesses that support the party's claims and defenses.250 in forming the opinions to be expressed. 251 (C) Expert employed only for trial preparation. A party may serve on any other party no more than 25 written interrogatories, including all discrete subparts. A party must, without waiting for a. 75 discovery request, serve on the other parties the following information regarding any person. Interrogatories must be served on the party from whom responses are sought and all other parties who have appeared in the action. Discovery requests (interrogatories, requests for production, or requests for admission) and responses are not filed with the court at the time they are served. Only answers to interrogatories must be verified.